Today increasing productivity is the most and effective ways to achieve economic growth. The purpose of this study is to analyze factors affecting labor productivity in producing major crops in central region of Mamasani Township in Fars province, Iran. Data were collected by filling up questioners through interviews with a sample of 358 farmers from 24 villages in Mamasani Township in farming year of 1386-1387 (2007-2008) who were selected by stratified random sampling. Factors that affected labor productivity were ages, experience, sex, level of education, farm size, participating in training extension programs, number of visits with extension men and access to credit. The analysis was done by using a multiple regression model. The results indicated that the level of education (primary school), farm size, degree of mechanization, membership in cooperatives, participating in extension programs, visiting of farm by extension men and village location had positive effect on labor productivity. Variables such as level of education of high school Diploma, experience, ratio of amount of loan to current costs had negative significant effect on labor productivity. The results of this research suggested that enlargement of farm size, increasing level of mechanization, extension and training program and farm visits by extension men should be encouraged and facilitated by the authorities and policy makers.