For rock-like materials, large diameter SHPB (Split Hopkinson Pressure Bar,SHPB) is necessary and essential in dynamic test. Based on the finite element software ANSYS/LS- DYNA, the transmission of different stress pulse waveform in large diameter bar was simulated and the loading waveform dispersion effect was investigated in this paper. Three typical stress pulses (rectangular waveform, triangular waveform and half-sine waveform) with the same duration time and maximum stress amplitude value were loaded on input bar of SHPB. The time-stress curves of different transmission distance on input bar were traced and recorded and four specific aspects were discussed respectively. Compared with rectangular waveform and triangular waveform, the results of numerical analysis indicated that there isn’t pulse waveform dispersion for half-sine waveform to transmit in large diameter SHPB and there is enough increased time to satify stress equilibrium before rock-like materials failure. The half-sine stress wave is able to meet the one-dimensional assumptions in the propagation process and can be used in large diameter SHPB test.