The Farmer Field School - FFS about crop composition conversion on rice land in Hau Giang province was organized to provide farmers with practical knowledge and to introduce new technologies. The purpose of this research is to measure the results of the FFS training course as well as to evaluate the improvements and new technique applied by the farmers after the course. Research results show that after the course, the farmers' relevant knowledge had been improved significantly with α=5%. It also shows that after the course, the cost of growing rice has been lowered as compared to that before the farmers joined the course. In addition, profit from growing rice is also higher after the farmers participated in the training course. When comparing profit margins, the research finds out that profit margin earned by farmers who participated in the training course is higher than the profit margin earned by farmers who didn't. However, after FFS training course, only few farmers conversed their crop composition into 2 crops of rice and 1 non-rice crop a year as recommended by FFS facilitators during the training course.