To improve the locus accuracy of linear motion mechanism with uncertainty factor,the analytical algorithm of locus reliability sensitivity analysis for linear motion mechanism is presented. First,by using the equidistant curve,the boundary of motion locus is constructed,taking account of the component size tolerance,the error analysis model of structure error and random error for the linear motion mechanism is proposed.The analytical equations for the statistical characteristic value of the motion error are derived by using the linearization method. And then the first order and second moment（ FOSM） method is applied to solve the locus reliability of linear motion mechanism,and the analytical model for locus reliability sensitivity analysis of linear motion mechanism is derived. At last,a numerical example of Hoeken mechanism is given.