In this paper，the arbitrary Lagrangian-Euler （ALE） method and penalty coupling method are used to simulate the processing of a helicopter with emergency floats landing on calm water. The influence mechanism of helicopter landing impact overload is expounded from the perspective of energy absorption mechanism. The influence law of different initial pitch angles on the impact overload of helicopter is revealed. Those results show that the vertical overload plays a dominant role in the helicopter landing impact process. With the increase of the pitch angle，the time of the peak impact appears delay，and the value of the peak impact increases. When the initial pitch angle is 10°，the peak impact increases from 8.83g to 18.89g compared with the case of the initial pitch angle is zero，with an increase of 115%. It is also found that the larger the pitch angle is， the lower energy-absorbing effect of the floats. And it leads to an increase in the peak impact value. When the initial pitch angle is 10°，the energy absorption effect of floats is reduced by 9.12% compared with the level flight.