Abstract: Based on the displacement discontinuity model for nonlinear deformation behaviour of fractures, the transmission rule of different normally incident elastic P-wave across multi-fracture is investigated. One-dimensional finite difference solutions of vibration velocity of transmitted wave are obtained by semi-numerical method to investigate the amplitude, energy, spectrum, and time delay of different wave's first-arrival pulses. Calculating results show that, in terms of transmission capacity of pulses, the wave ranked from large to small is rectangular wave, half-sine wave and triangular wave. Velocity transmission coefficient, energy transmission coefficient and frequency-domain amplitude of higher harmonic wave increases with the increasing of incident wave amplitude. Time delay decreases with the increasing incident wave amplitude, and triangular pulse's time delay is larger than half-sine pulse's time delay. Velocity and energy transmission coefficient gradually decrease with a slower speed. Frequency-domain amplitude of higher harmonic increases in the early stage and then decreases gradually with a slower speed. The increase of time delay accelerates with incident wave transmitting across more fractures.