Abstract This study aims to identify the impact of (K.W.L.H) Strategy on fourth –scientific students comprehending of physics concepts and acquiring metacognition skills . to verify this aim ,the researcher sets two main null hypotheses : 1- There is no statistical difference at (0.05) level of significance ,between mean score of the group of the study in comprehending physics concepts according to the variables ; method , gender and interaction between them . 2- There is no statistical difference (0.05) level of significance , between the mean score of the students in the groups of the study in acquiring metacognition skills according to the variables : method , gender , and interaction between them . The study is limited to the students at fourth- scientific classes in Nineva schools / zummar and AL-Iyatheya branches for the academic year 2011- 2012 . The researcher uses the factors Design (2 x 2) of two independent variables at the same time : method of teaching and gender , and with two levels. This design includes four equivalent groups divided between the two variables . Two of those groups represents the experimental groups (male , female ) . They have been taught physics by using (K.W.L.H) Strategy . The other two groups represents the control ( male , female ) . They have been taught physics by using the traditional method . The sample consists of(107) male and female students distributed among four groups including ( 25,25,25,32) students .Those groups have been equivalent in some variables such as age ( measured in months) , students marks in physics for the preceding academic year , Intelligence quotient , and parents academic level . The researcher prepared two objective tests . The first one has assigned to measure students comprehension of physics concepts , including (30) multiple – choice items of four chooses The second one has assigned to test metacognition skills including (17) multiple-choice items of three chooses . The tests are valid , reliable , and discriminated . The researcher also prepare the tacking plans for the two groups of the study (experimental and control) and they have been given to the teachers of physics who take part in this study . The experiment started on 10th , Oct. and lasted till 22nd , Dec. 2011. The two tests have been administered on the groups after finishing the experiment . The data have been collected and analyzed statistically by using (ANOVA) two-way test . The results revealed the following : 1- There is statistical difference , between mean scores of students in the two groups concerning comprehending physics concepts , due to the method of teaching and for the benefit of(K.W.L.H) strategy . 2- There is statistical difference between the mean scores of the student in the two groups concerning acquiring metacognition skills due to the method of teaching and for the benefit of (K.W.L.H) strategy and also due to the gender for the benefit of female students . In the light of the findings above , the researcher sets many recommendations : 1) Teachers of physics should train to use metacognition skills to help their students comprehending physics concepts and metacognition skills. 2) Physics subject for preparatory stage should include activities that promote metacognition skills. 3) The (K.W.L.H) strategy can be used in teaching physics for fourth –scientific class as it has impact on students comprehension of physics concepts promoting students metacognition skills . The researcher also suggests the following studies as completeness for the current study : 1- Comparing three strategies in acquiring physics concepts for the fifth scientific students and developing their metacognition skills. 2- The impact of (K.W.L.H) strategy correcting mis- comprehending physics concepts for second intermediate schools student and developing their attitudes towards physics .