This paper systemically presents a theoretical analysis on pump source angle tuning in quasi-phase matched (QPM) optical parametric oscillator (OPO) in periodically poled crystal. The precise formula and the formula in paraxial approximation, both of which describe the relationship between rotation angle of pump source and wavelengths of pump, signal and idler wave in QPM OPO, are presented. It is found that the idler wave and the pump wave for signal-resonated OPO propagate along the same side of the crystal x-axis to exit, as propagate the signal wave and the pump wave for idler-resonated OPO. In addition, the separation angle between the signal wave and the idler wave for signal-resonated OPO is greater than that for idler-resonated OPO. More importantly, the tuning rate for signal-resonated OPO is also greater than that for idler-resonated OPO.