Abstract: Based on grain yield statistical data for 1949~2006 in Guangdong Province, total grain yield tendency and main mechanisms including per unit area grain yield, cultivation area, planting structure, multiple-crop index, agricultural technology and agricultural investment were analyzed. The results show that total grain yield for Guangdong Province increases fluctuatively with population growth and industrial development. Arable land area and grain-crop cultivation area have a decreasing trend since 1949. The reasons for the above trends are as follows: (1) the increase of the main affecting factor of production, per unit area grain yield, results in steady growth in total grain output; (2) cultivation area of rice, the main grain-crop, is not change greatly and the yield per unit area increases year-on-year; (3) improving multiple-crop index increases grain production even though arable land area decreases; (4) advancing agricultural technology such as pesticide and fertilizer application, improved farm mechanical power, and increased agricultural investment promote food production.