Abstrak
This research the reseacher found that Some of the problems were: students find it difficult to memorize new vocabulary,the students preferred to use indonesian language during the teahing and leraning process than English in general the students had difficult to understand learning English. This research used a quasi-experiment using non-equivalent control group design. The samples used were class VII D as experimental class consisted of 33 students and VII E as control class consisted of 33 students. The results of this research for the first hypothesis using a paired sample t-Test, it was found that Sig (2-tailed) 0.05, so the hypothesis alternative (Ha) was accepted, indicating that there is a significant effect of using the four square strategy. Next, for the second hypothesis using a independent sample t-Test, it was found that Sig (2- tailed) 0.05, so the hypothesis alternative (Ha) was accepted, indicating that there is a significant difference between the class that used four square strategy and the class that do not used four square strategy. And for the third hypothesis using a independent sample t-Test, it was found that Sig (2-tailed) 0.05, so the hypothesis alternative (Ha) was accepted, indicating that the vocabulary mastery of students who use the four square strategy was better than that students who do not used four square strategy. So, it can be concluded that the four square strategy had a effect on students vocabulay mastery.