The research aims to identify the effect of the training program on the special physical abilities and some biomechanical variables of the skill of Flat Service in tennis, and the two researchers used the experimental approach to designing the one group in the pre and post measurement method. Sample included (5) tennis players under (16) years, and the program was implemented at (4) units per week with (32) daily training units during the application period, and after the completion of the application of the training program under discussion, the Dimensional measurements, then performing the motion analysis of the study sample and statistically processing the data then presenting and discussing the results The most important results were that there were statistically significant differences between the pre and post measurements in the special physical abilities and the skill performance of the skill in question and in favor of the post measurement, as there were no statistically significant differences between the pre and post measurements in the biomechanical variables under consideration. Key words: Tennis - Flat Service – Biomechanical variables – Special physical abilities.