This study aimed to investigate the effect of using McCarthy Model in development reflective thinking and science achievement among grade 6th female students. The sample of study consisted of (55) female students of 61 grade, which were selected from two schools in Dakhiliyah Governorate. The experimental group (N=31) was selected from Welayate Bid Bid School (5-12) which was taught the science content by McCarthy Model and control group (N=24) was selected from Sroor Basic school (5-12) which was taught the science content by the conventional method of teaching To achieve the study's aims, three research instruments were designed: a teacher guide based on McCarthy Model, a reflective thinking skills test and a science achievement test. The validation of the study instruments was assessed by a group of jury members. The reliability of reflective thinking skills test was (0.72), whereas the reliability of science achievement test was (0.86). Results revealed that there were statically significant differences at (a=0.05) between the means of the experimental group and the control group in conclusions and providing convincing explanations skills and in the whole reflective thinking skills in favour of the experimental group. The study also showed that there were statically considerable significant differences at (a= 0.05) between pre and post reflection thinking skills in visual vision, conclusions and provide convincing explanations skills and in the whole reflective thinking skills in the experimental group. In addition, the study showed that there were statically significant differences at (a=0.05) between the experimental group students and the control group students in application, inference levels and in the whole science achievement test in favour of the experimental group. Accordingly, the study recommended the need for conducting workshops and training workshops for science teacher on how to use McCarthy Model in science classes. It also proposed conducting similar studies of the current study, but on other variables such as creative thinking, investigates misconceptions in students and type of students questions in science class.