Base on analysis of the import and export situation of Chinese watermelons from 1991 to 2011,the changes of the Constant Market Share Model was used to analyze multiple products and markets to single product one,the increase factors between 1997~2011 in 3 decomposed periods were analyzed.The results showed that market scale effect,market distribution effect and competitive effect made different effect to Chinese watermelons export,compared with last period,market scale effect was negative in second and positive in third period for Chinese watermelons export,meanwhile,competitive effect was opposite；market distribution effect was always positive for Chinese watermelons export,but showed the downward trend.