Using split-step Fourier transform method, the authors performed the simulation on supercontinuum generation (SCG) of femtosecond laser in nanofiber. The effects of diameter of the nanofiber, peak power and input pulse duration on the supercontinuum generation were analyzed. The results show that the higher the peak power of the input pulse, the easier the supercontinuum generation could be observed; the narrower the input pulse, the wider the light spectrum width. The dimension of the nanofiber plays an very important role in supercontinuum generaion of femtosecond laser pulse, the supercontinuum generation is not inversely proportional to the diameter of nanofiber, and there is a optimum diameter of nanofiber for the certain input laser pulse, so that the supercontinuum generation can be noteworthy. The obtained results in this paper would be helpful for further research on and making use of the supercontinuum generation in nanofiber.