Abstract: Aiming at the problem that the number of signal transmission paths increases and the performance of physical random access preamble signal detection decreases, this paper proposes an optimal detection statistical algorithm. The time-domain correlation detection was performed on the received signal at the antenna end and the local ZC sequence. The optimal detection statistics were derived through the maximum likelihood function and the signal power delay spectrum. It was compared with the threshold value for peak detection. The simulation results show that when the signal is transmitted in the 5G TDLA30 channel, compared with the traditional peak detection algorithm, the preamble detection performance is improved by more than 1.5dB.