The objectives of this research are 1) to develop Web-based Computer Assisted Instruction using inquiry-based learning to promote computational thinking skill on logical and function programming for 8th  grade students 2) to identify effectiveness and compare learning achievement of the Web-based Instruction developed, 3) to compare learning achievement pre and post applying the Web-based Instruction developed, 4) to determine computational thing skill on logical and function skill of the learners using the developed Web-based Instruction and 5) to achieve learners’ satisfaction whom studied with Web-based Instruction.  Research tools used for this are consisted of the developed lesson on the Computer Assisted Instruction, achievement test, and Computational Thinking Skill assessment form and satisfaction survey. The representative sample during this research is 46 grade 8th students from Triamudomsuksanomklao School (second term of 2019 academic year) which was drawn from simple randomization using classroom.
The result of this research shown that the developed Web-based Instruction has the effectiveness of 85.70/80.28 which is higher than the standard criteria set at 80/80, academic achievement of learners has increased significantly, statistically at 0.05, learners’ Computation Thinking Skill has developed into good level and the learners are satisfied with the Web-based Instruction in high level.