Weight on Wheel(WOW) signal is an electrical signal which plays an important role in confirming the air/ground condition of the airplane during landing phase. The time to trigger the WOW signal has important influence on the working condition of aircraft systems. Preliminary dynamic model from touchdown to the WOW signal is triggered was established according to dynamics method. Based on the dynamic model, the impact of landing status was analyzed. This model may have some reference value on the design of related aircraft systems.