This study aims to construct a teaching strategy, investigate the effectiveness of the suggested teaching strategy on mathematical proof concept and geometric proof writing skills. This suggested strategy is composed of four steps which consist of a lot of instructions and these steps are as follows: • Understanding the problem • Production, formulation and exploration, a conjunctive • Selection and organization arguments into a deductive chain • Organization and writing arguments into an acceptable proof and approaching a formal proof. The suggested strategy is supposed to be consistent with the following principles, the importance of argumentation, Paolo Boero's argumentation model, proof scheme, proof thinking methods, knowledge structure, the method of presenting mathematical generalizations, geometric thinking levels of Van Hiele, grading in geometric representation, colour usage, proof flow chart and proof function. To measure the effectiveness of the suggested strategy, the researcher has chosen a sample of (132) grade nine female students and divided them into two equivalent groups: control and experimental groups. Each group contains 66 students. The experimental students studied the triangle geometry unit using the suggested strategy, but the control group studied the same unit using the traditional method. At the end of the experiment, two tests, prepared by the researcher, were applied: mathematical proof concept test which contains (28) items distributed among (14) principles. The Geometric Proof Writing Test contains (9) items which measure (9) skills of the Geometric Proof Writing Skills. The results of the statistical analysis showed the following: There is no statistically significant difference (at level of a < 0.05 among the average marks of the students of the experimental group and the students of the control group concerning the dimensional application of the Mathematical Proof Concept Test. There is a statistically significant difference (at level of a < 0.05 among the average marks of the students of the experimental group and the students of the control group in the Geometric Proof Writing Test in favour of the experimental group. The study concluded some recommendations in the light of the results including: merging the principles of strategy structure in the academic curricula while preparing them and reorganizing some of the units in the light of the suggested strategy and develop the suggested strategy to concentrate on the proof concept of the student