We numerically investigated four-wave mixing (FWM) and supercontinuum generation in photonic crystal fibers (PCFs) in the long pump pulse scheme for the first time. We showed that simply based on phase-matching condition and energy conservation with quasi-continuous-wave approximation, one can theoretically determine the FWM signal and idler wavelengths with pump in the normal-dispersion regime, and the two symmetrical modulation instability sidebands with pump in the anomalous-dispersion regime. Using adaptive split-step Fourier method, we quantitatively simulated FWM and supercontinuum generation in PCFs with different dispersion profiles when pumping with a 1064 nm sub-nanosecond laser. Our simulation results agree with the experimental results very well.