An on-line monitoring method of primary frequency characteristic parameters for generators， based on dynamic measurement data sampled by synchronized phasor measurement unit（PMU） in wide area measurement system（WAMS） is presented. First， identifying occurrence of frequency disturbance by real-time monitoring of the power grid frequency， the multi-criterion is used to distinguish large or small frequency disturbance. Then， different methods are adopted to compute unit PFR parameters such as: generator frequency bias coefficient， dead band and delay time， which can be used to assess the generator's primary frequency regulation（PFR） performance， and provide data for its evaluation. Finally， the method is verified with the WAMS practical project implementation.