Long-term alternating loads on the connecting bolts of hydro-turbine head cover,which results in fatigue damage causing many serious accidents.Therefore,it is necessary to carry out in-depth study on the calculation method of fatigue life of head cover bolts in order to improve the accuracy of fatigue life calculation.In order to solve the above problems,a method for calculating the fatigue life of Turbine head cover bolts based on combination of power density and short-time Fourier analysis（PD-STFA） is put forward,with emphasis on the influence of coupling action of loading frequency and amplitude load on the fatigue life of head cover bolts.Firstly,the position and stress of dangerous section of connecting bolt are calculated by finite element method;secondly,the average stress of contact surface of bolt head is measured by strain-based hollow pressure sensor,and then the measured average stress of contact surface of bolt head is transformed into the stress of dangerous section according to generalized Hooke’s law;finally,based on linear damage accumulation theory,the fatigue life of the head cover bolts is calculated by PD-STFA method and the traditional rain flow counting method.The calculation results show that the fatigue life of the head cover bolts is 1.966× 10~5 h based on PD-STFA method and 4.113 ×10~5 h based on traditional rain flow counting method.According to the investigation of power plant users,the calculation results based on PD-STFA method are closer to the actual service life of bolts for about 30 years,and can predict the fatigue life of the turbine head cover connecting bolts more accurately,thus providing theoretical guarantee for the safe and stable operation of the hydro-turbine.