A method for time source calibration, wherein the method comprises steps of sending a requirement for obtaining time by a client side computer to a server side; sending a first data packet including time and generated verification information by the server side to a key device via the client side computer; said time is the current time of the server side; calibrating time of key device with the obtained as benchmark time and counting time normally by the key device; sending a second data packet including calibrated current time of the key device and the verification information by the key device to the server side via the client side computer; and obtaining the current time of the key device in the second data packet by the key device after the verification information in the second data packet is verified to be valid by the key device. According to the present invention, the reliable time source is obtained, which secures the security of the trade.