Based on panel data of 14 manufacturing enterprises during 2005—2008, after analysis of self-selection effect and learning by export effect from manufacturing enterprises export, the results show that the relationship between Chinese manufacturing enterprises export and productivity violates heterogeneous enterprise trade model, that self-selection effect is not obvious, that there is "productivity paradox", and that learning by export effect is not significant. Although there is positive correlation between productivity and export scale of export enterprises, there is negative correlation between productivity and export scale after other variables influencing export scale are controlled, meanwhile, when other variables influencing productivity are controlled, export scale is also negatively related to productivity. The cause of insignificant self-selection effect of China’s enterprise export lies in the inconsistence of processing trade and realizing condition with classic theories, while the main reason for unobvious effect of learning by export results from unclear self-selection effect and scale profit degression of export enterprises.