AbstrackThis study is to find out whether the use of Group   investigation (GI) method in studets’ reading comprehension is effective or   not. This   research was done on the student of the ten grade, Senior High School in SMK   N 2 Kediri, which  have  three    classes. The ten grade of SMK N 2 Kediri was divided into three   classes. There were class X A, X B, and X C. the researcher used X C as an   experimental class and X B as control class. Reading test was the data which is collect as an   instrument. Kuder Richardson 21 formula was used to get reliability. The result was 0.81, so  the test was reliable. ANCOVA was used to   analysed the data. The result of the analysis indicate that the students’   reading comprehension ware significanly higher. The result 0.002 it is lower   than 0.05 (0.000<0.05). it is conclude that using Cooperative Group   Investigation is effective in students’ readingcomprehension.Keywords: reading comprehension, group Investigation (GI).