Abstract: According to the per unit area grain yield data from 1993 to 2004, it was clear that per unit area grain yield took on an increasing trend on the whole. By Cobb-Douglas production function, the factors were analyzed of per unit area grain yield in whole province since 1990s.The result indicated that during the year of 1990—1997 and 1998—2000 the biggest contribution on increasing per unit area grain yield was the devotion of agricultural science and technology, its value was respectively 17.64% and 9.68%; during the year 2001—2004 the stricken area was the mostly factor on decreasing per unit area grain yield, and the value was 48.94%. From the whole trend, the devotion of agricultural science and technology was the most important factors for driving per unit area grain yield, its value was 44.50%. Thereby, relying on agricultural scientific progress to continuously increase the ability for grain integrative production will be the primary instrument and channel.