The invention provides a non-data aided OQPSK (Offset Quadra Phase Shift Keying) signal closed loop carrier synchronization method. The square spectrum characteristics of an OQPSK signal are utilized, a square spectrum estimation based carrier frequency offset coarse estimation algorithm is adopted, and accordingly the range of the frequency of the signal can be effectively reduced. A carrier synchronization loop is of a dot product and cross product frequency discriminator and phase discriminator combined cross ring structure and accordingly the speed and the accuracy of the carrier synchronization can be ensured simultaneously. A proportional integral filter is adopted as a loop filter to enable the synchronization loop to be a second-order loop and accordingly the stable loop dynamic response can be implemented under the conditions that the direct current gain is infinite and the frequency offset is a constant. According to the non-data aided OQPSK signal closed loop carrier synchronization method, the frequency offset can be accurately estimated, the accuracy and the speed of the carrier synchronization can be ensured, and the recruitments of a communication system can be met through the combined utilization of a dot product and cross product frequency discriminator and phase discriminator on the basis of the square spectrum frequency offset coarse estimation.