In the drop test for nose gear of a certain type of unmanned aerial vehicle, unu sual fluctuation of load is spotted when ground load increases. The relations be tween landing damper compression and ground load in the drop test are analyzed, and the conclusion goes that the main oil hole of the damper is too small to enable bubbles to move from main chamber to the air chamber. Landing gear drop test dynamics model including the effect of main oil chamber cavitations is built. The dynamics characteristics of the specific model are studied through numerical analysis, and the results are consistent with test results. After cavitations inthe main oil chamber are eliminated, the results of actual drop test are quite similar with those of theoretical simulations using cavitationfree model. By comparing two methods of drop test, the conclusion is that axial load fluctuation is caused by cavitation. As soon as the cavitation is eradicated, the peak value of the vertical land load decreases by 0.3 kN, and the damping efficiency of theentire landing gear structure increases by 2%.