Harmonic components of the geared four-bar Linkages for coupler path with prescribed timing are analyzed in this paper. The internal relations between the coupler path and Side Link Swing-Angle Operator(in short
SLSAO) are discussed. The mathematic formulas applied to compute the real size and installing dimensions of the linkages are established. A dimensional synthesis method of coupler path is put forward by setting up the numerical atlases of SLSAO and making use of fuzzy identificatoin. Finally