An effective approach was developed for identifying and correcting ocean‐bottom seismometer (OBS) time errors through improving ambient noise cross‐correlation function (NCCF) analysis and combination with other methods. Significant improvements were illustrated through analyzing data from a passive‐source seismic experiment in the southwestern sub‐basin of the South China Sea. A novel method was first developed that can effectively identify errors in the sampling frequency of the OBS instruments. The traditional NCCF method was then expanded by increasing the analyzed data spectrum from a single‐frequency band to dual‐frequency band pairs, thus doubling the number of available data points and substantially improving the time correction quality. For data with relatively low signal‐to‐noise ratios, the average time errors were reduced from the original average values of 60–80 ms by the conventional methods to using the improved approaches. The new multistep procedure developed in this study has general applicability to analysis of other OBS experiments. The demonstrated significant improvements in the data quality are critical for advancing seismic tomography and other modern marine geophysical studies that require high accuracy in the OBS data.