Abstract: The inducer is an important component for liquid rocket engine turbopump.The inducer is often accompanied by cavitation of different degress and modes during operation.The turbopump characteristic and reliability is influenced seriously by flow impulse and mechanical vibration caused by cavitation.Nonsymmetrical cavitation is a type of complicated flow phenomenon which exists in turbopump head decreasing.The characteristics of nonsymmetrical cavitation flow in inducer during head descent of cryogenic medium turbopump has been studied by means of visualization test system and numerical simulation.By comparing the experimental observation and numerical calculation results,it is found that nonsymmetrical cavitation of the inducer is the excitation factor leading to the drop of turbopump head.Meanwhile,the relationship between nonsymmetrical cavitation and flow instability has been studied systematically by employing test observation and numerical calculation.