A logging system and method based on a one-way hash function are described. The system includes a user system, a trusted third party, and a verifier. The method includes the following steps. The user system records a log file and initializes a message authentication code key and an image code. When the verifier requests the user system for a logging unit corresponding to an operation history, the user system uses a one-way hash function to calculate a check value and returns the check value and an image code sequence. The verifier then verifies the integrity of the check value and the image code sequence through the trusted third party. The trusted third party checks if the image code sequence obtained by the hash calculation equals to the check value through the one-way hash function, so as to verify that the log file of the user system has not been modified.