The sensitivity model of multivariate detection is studied,and the model is derived and established by using the detection signal-to-noise ratio,detection probability and false alarm rate.The accuracy of the model is proved by experiments.On this basis,the influence of APD unit number,pulse accumulation times,fill factor and dead time on detection sensitivity under different detection conditions is analyzed,which provides theoretical foundation for the selection of multivariate APD.The results show that:1) When the pulse accumulation number is 6,the larger the fill factor,the smaller the dead time and the better the ranging performance;2) Under high background noise,increasing the number of APD units can significantly improve the detection sensitivity;and 3) Under low background noise,4-unit APD can achieve better ranging effect.