Applying the timing recovering loop for PCM/FM to Multi-Symbol Detection(MSD) could reduce the complexity of the whole system. This paper proposes a symbol timing synchronization algorithm for MSD in telemetry Pulse-Code Modulation/Frequency Modulation(PCM/FM) system. The proposed algorithm uses the likelihood ratio of MSD as the statistical variable for timing estimation, and can adopt traditional timing synchronization loop in PCM/FM using limiting amplitude and frequency discrimination to achieve symbol synchronization. Compared with the traditional MSD symbol timing synchronization method based on the “early-late gate”，the proposed method saves the operation of a branch of MSD, which greatly reduces the storage and computing resources in receiver. In addition, the proposed algorithm adopts the Gardner algorithm as a timing error detection unit, which facilitates high speed implementation in practical systems. The normalized variance of the timing estimation error in the proposed method is still less than 0.01 in the low SNR region, which satisfies the requirements of the telemetry receiver. Compared with the ideal synchronization situation, the proposed algorithm has almost no loss in terms of Bit Error Rate(BER) performance, and has a promising prospect.