The invention relates to an implementing method of frame synchronization in the orthogonal frequency division multiplexing system, including the following steps: firstly using the received data for a cross-correlation arithmetic with the local storage short sequence, choosing a datum with a short training length when glidingly backwards a datum every time, wherein when the correlative value is maximum, the received datum is an integral short training symbol, and giving out a starting position of the short training symbol; and then, calculating the time-delay correlative value of each datum with a short training length, according to the given starting position; continuously performing time-delay related arithmetic to the each received datum with a short training length, and giving the starting position of a long training sequence when the correlative value is smaller than the threshold value. The method can greatly reduce system resources on the basis of guaranteeing frame synchronization precision.