Aiming at the problems of signal demodulation in 5 G downlink Orthogonal Frequency Division Multiplexing（OFDM） system due to Doppler frequency shift and frequency error caused by the non-synchronized transmitter and receiver crystal oscillators

a Primary Synchronization Signal（PSS） and Secondary Synchronization Signal（SSS） combined frequency offset estimation algorithm is proposed. Firstly

the cross correlation values of the PSS and SSS at the receiving end are calculated with the local PSS and SSS

respectively. Then

the PSS cross-correlation result of the first synchronization signal and Physical Broadcast Channel（PBC） block is used to calculate the initial frequency offset value with the SSS cross-correlation results of the second SSB block. Finally

we use the PSS cross-correlation results and SSS cross-correlation results in the same SSB block to perform cross-correlation calculations to calculate the new frequency offset value

and also use the initial frequency offset value to correct its polarity to obtain the final frequency offset. Compared with the PSS-based frequency offset estimation algorithm

this method uses PSS and SSS for joint frequency offset estimation to improve the accuracy of the algorithm

and expands the estimation range from [-3.5

3.5] kHz to [-7.0

7.0] kHz.