Aiming to the problems existing in the applications of clocks received via global position system（GPS） receiver or generated by crystal oscillator， clock error models are respectively established. Based on the error estimation， a new method of producing clock of high synchronous accuracy is proposed. According to the estimated error state， the synchronous clock equipment based on the proposed method can choose an appropriate way to produce clock of high accuracy under all kinds of operation conditions， so the synchronization reliability is improved remarkably. The equipment has accurate pulse per second output and real-time time message output， thus it can be used to achieve a good realization of time synchronization in substations.