– This study aimed to describe the effectiveness of the application of learning models investigative group to improve science process skills and critical thinking skills of high school students. The method used is quasi-experimental with a given experimental class treatment with the application of investigative learning and classroom control group with conventional learning methods practicum. The results showed that the group of Investigation learning model can significantly improve the students' science process skills compared with conventional methods of practical learning model. Data were getting N-gain experimental class was 0.58; and N-gain control class 0,49. N-gain experimental class and control class fit into the category of being. While the critical thinking skills of students, the results obtained from this study is Critical Thinking Skills of students did not differ significantly in the experimental class with grade control. Data were getting N-gain experimental class of 0.01; and N-gain control class is 0.01. The N-gain in the low category. N-Gain very low state that the investigation group learning model can not be set as the cause of increasing students' science process skills.