The invention relates to a method and a system for synchronously inserting network time. The method comprises the following steps: S1, a client generating an NTP (Network Time Protocol) timestamp query information packet and sending the NTP timestamp query information packet to an optimal time server, wherein the optimal time server is a time server selected by the client according to an optimal time server algorithm; S2, the client receiving an NTP timestamp answer information packet generated by the optimal time server according to the NTP timestamp query information packet; S3, repeating S1 and S2, and executing S4 when the repeated times is N, wherein N is more than or equal to 5 and less than or equal to 10, the repeated time interval is t, and t is more than or equal to 10s and less than or equal to 30s; S4, the client calculating a time difference data mean by adopting an information packet filter algorithm; S5, the client calibrating the client time according to the time difference data mean; and S6,the client displaying the calibrated client time. By adopting the method and the system, the calibrating precision is high, the system is small, the scheme is easy to realize, and the hardware cost is relatively low.