For the problem of system timing synchronization inaccuracy caused by impulsive noise in Multiple-Input Multiple-Output (MIMO) Power Line Communication (PLC), an Orthogonal Frequency Division Multiplexing (OFDM) symbol timing synchronization algorithm based on MIMO PLC system is proposed in this paper, which uses differential correlation and Maximum Ratio Combining (MRC) to improve the synchronization performance. Under 2×2 MIMO PLC channel model, the two transmitting ports send preamble sequences with good autocorrelation and cross-correlation characteristics. At the receiving end, the impulse noise in the power line is filtered by setting the threshold, and the timing coarse synchronization is realized by using the improved delay autocorrelation algorithm. Next, the window summation method is used to reduce the estimation range of fine synchronization. Then, a combined differential correlation and MRC algorithm is used in the timing fine synchronization stage, which has 2 dB improvement compared with the previous method. The simulation shows that the synchronization performance of the proposed method is obviously superior to the traditional cross-correlation method.