The purposes of this research to produce learning materials by using Cooperative Learning Model Group Investigation Type that valid, effective, and practical to improve high order thinking skills of junior high school students. The study was conducted in two phases, the development stage of learning materials adapted to the 4-D model and the classroom implementation stage with 38 students by using the onegroup pretest-posttest design. Data analysis result are: (1) Validity of learning materials based on: (a) Validation of the materials have very good category, (b) Readability of handout and worksheet are easy for students to understand; (2) Efectiveness of learning materials based on: (a) The response of students are very strong, (b) High order thinking skills of students improvment with high category of N-Gain; (3) The practical of learning materials based on: (a) Feasibility of instructions have very good category, (b) Students activities have active category, (c) Constraint of learning can be overcome. The conclusion of this research that development of learning materials by using Cooperative Learning Model Group Investigation Type are eligible to improve high order thinking skills of junior high school students.

Keywords : Learning Materials, Group Investigation, High Order Thinking Skills.