The invention relates to time synchronization technical field, and discloses a conversion method of network time protocol, the method provided by the invention specifically comprises the process: NTPclient sends the time synchronization request datagram to protocol adapter, which then transforms the synchronization request datagram to time delay request datagram, and then send the time delay request datagram to a PTP main clock server, the PTP main clock server will produce response datagram and transfer the response datagram to the protocol adapter, which converts the response datagram to NTP time synchronization response datagram and sends the NTP time synchronization response datagram to NTP client, after receiving time synchronization response datagram, the NTP time synchronization response datagram is analyzed by the NTP to achieve time synchronization. NTP time synchronization precision is enhanced through the above mentioned technical scheme, and the demand on network time synchronization precision is met by combining with the features of PTP and NTP, the synchronization precision can be guaranteed, the deploy is simple, the invention also discloses a network time protocolconversion system.