In this paper, we numerically study the soliton trapping of supercontinuum in photonic crystal fiber by solving generalized nolinear Schrödinger equation. Using the cross-correlation frequency resolved optical gating (X-FROG) technique, the propagation of the supercontinuum is recorded along the fiber and the evolution of soliton trapping is observed. When the phase-matching condition is met, new frequency of the pulse trapping is generated from four-wave mixing of soliton with nonsolitonic radiation, and is continuously blueshifted while the soliton is redshifted. Higher pump-power shows the strong interaction between soliton and nonsolitonic radiation. Provided in the paper is a theoretical basis for tunable ultra-short laser pulses and supercontinuum researches.