A method and apparatus for performing real time clock (RTC) calibration through frame number calculation are provided, where the method is applied to an electronic device. The method includes the steps of: before power failure of the electronic device occurs, obtaining an original time value from an RTC of the electronic device and storing the original time value and a frame number of a first frame into a storage unit; and after the electronic device is powered on since elimination of the power failure, obtaining a frame number of a second frame and performing at least one calculation operation according to the frame number of the second frame, the frame number of the first frame, and the original time value to determine a calibrated time value of the RTC, and updating the RTC with at least one of the calibrated time value and a derivative of the calibrated time value.