Disclosed is a robust downlink timing synchronization method in an LTE system, which includes: step 1: a receiving terminal continuously storing time domain signal sequences of M PSS transmission periods; step 2: performing narrowband filtering on the time domain signal sequences of the M PSS transmission periods; step 3: performing down-sampling on data obtained after the filtering; step 4: performing sliding differential mirror correlation on the down-sampling data of an m th PSS transmission period to obtain a correlation value of an i th instant; step 5: superposing correlation results to obtain a superposition result; and step 6: determining whether the superposition result has an obvious peak interval; if yes, completing capturing the primary synchronization signal, and obtaining timing information according to a position of a maximum correlation peak; otherwise, returning to step 1. The present invention effectively reduces the influence of initial frequency offset and ensures the timing synchronization in a low signal-to-noise ratio interval. The present invention has fine utility under the receiving conditions where the initial frequency offset is not compensated and the channel transmission environment is unknown, and has good robustness.