FIP-fve is a low molecular-mass protein identified from Flammulina filiformis， which has many biological activities including immunomodulation. Our previous studies found that FIP-fve had certain growth-promoting effect on F. filiformis mycelia. We constructed an over-expression vector pCAMBIA1301-pGPD-FIP-fve， and transformed it into Agrobacterium tumefaciens LBA4404 strain to study the native biological function of FIP-fve to F. filiformis. FIP-fve gene overexpressed F. filiformis was obtained via Agrobacterium transformation. By comparing the biological characteristics of FIP-fve gene-silent F. filiformis （RNAi：FIP-fve）， FIP-fve gene-overexpressed F. filiformis （pGPD：FIP-fve） and wild F. filiformis （CK） in mycelium and fruiting body stages， we found that the growth speed of pGPD：FIP-fve was faster than that of CK， whereas the growth speed of RNAi：FIP-fve was the lowest. After cultivating the fruiting body， yield-related traits of pGPD：FIP-fve were significantly better than that of CK in terms of fruiting body numbers， stalk length， fruiting body yield and biological efficiency， and those traits of RNAi： FIP fve were the worst. It is indicated that FIP-fve significantly promote the growth of F. filiformis mycelia and affect the final yields of F. filiformis.