The purposes of this research were to create and evaluate the effectiveness of Computer Assisted Instruction about Tensile test The CAI consisted of 9 lessons The sample was 20 first year diploma students in Tool and die make Department Faculty of Production Technology. Rajamangala University of Technology Phra Nakhon. First of all the students did the pre-test and then they studied via CAI. After that they did the post-test. After using CAI the result was evaluated to find effectiveness and learning achievement was analyzed. The finding showed that CAI effectiveness reached the standard of 90/90 Further more the students knowleage increased at significant level of 0.01