The dimensional constraint conditions of a kind of geared five-bar crank-slider mechanism (GFBCSM) were analyzed. Mathematic model of coupler path has been established based on complex vector theory and Fourier series theory. The mathematic equations for calculating actual dimensions of mechanism, coupler’s point position and mechanism installation parameters were derived. Several numerical atlas databases of harmonic characteristics of coupler rotation-angle operators have been set up for transmission ratio i=-1, ±1/2, ±1/3 between the crank and the coupler. Dimensional synthesis of coupler path of GFBCSM has been realized by using the numerical atlas method, and the given example showed that the method is efficient and feasible.