A new database was established, including the indexes such as different mycorrhizal types, net primary production(NPP) and average annual precipitation(MAP) of forests, based on the global forest database. The new database was used to study the responses of NPP of the forests to MAP change. Of all forests dominated by six different mycorrhizal types, the total NPP, aboveground NPP and tree leaf NPP increased with increasing MAP. However, the belowground NPP, stem NPP, and fine and coarse NPP presented a trend of either increase or decrease with the enhancement of MAP in the forests. As far as the responses of forest total NPP to MAP change concerned, the highest explanation(31.79%) of MAP change to the variation of total NPP was observed in the forest dominated by arbuscular mycorrhiza+ecto-mycorrhiza type. Contrarily, the MAP change only explained the 4.85% of the variation of total NPP in the forest dominated by ecto-mycorrhiza+ectendomycorrhiza type, which was the lowest explanation in all the six forests. We conclude that different mycorrhizas affect the extent of response of forest NPP to MAP change. Mycorrhizal type is an important index for accurate prediction of future change of forest NPP with change of precipitation.