Abstract: The parameters of the gear pair mechanism in the underwater detection device of the spent component are uncertain.Under the seismic condition, the structure may be randomly vibrated and may fail.In order to evaluate the failure probability, the key gear pair mechanism in the underwater detection device of the spent component was firstly calculated by the finite element analysis software ANSYS to calculate the response of the structure under earthquake, and then the multiple finite element analysis iteration was combined with the uncertainty parameter.The Kriging model of 3σ stress including a gear shaft radius, peak power spectral density, axial elastic modulus and stress under random vibration was established and the structural failure probability was calculated.Finally, the probability density curve of the model 3σ stress was obtained by kernel density estimation.The calculation results show that the 3σ stress in 200, 370 MPa within the interval probability density is higher, in the lower interval probability density on both sides the failure probability of the gear pair mechanism is low, and the probability density of the model 3σ stress is consistent with the engineering experience.