Disclosed is a time synchronization method and apparatus. The method includes: receiving a time synchronization message sent by an upstream device through a clock port; obtaining a message rate parameter in the time synchronization message; according to the message rate parameter, correcting a time synchronization message loss detection parameter of a slave clock port, wherein the time synchronization message loss detection parameter is used to detect whether the time synchronization message is lost; and according to a correction result, keeping clock synchronization with the upstream device.