The invention relates to a seismic data time-depth conversion method, and belongs to the field of seismic data processing technology of oil exploration. The seismic data time-depth conversion method comprises the steps of acquiring seismic data and well data of a work area to be evaluated, determining a time domain seismic data volume after match and an interval velocity after smoothing along a layer, establishing an interval velocity data volume after VSP velocity constraining, and generating a depth domain seismic data volume through the time-depth conversion method. Through a VSP corridor stacked section and the VSP velocity constrained seismic data, the invention establishes the interval velocity data volume varying along a reflective layer in the entire work area, eliminates the problem of low time-depth conversion precision of seismic data due to that a conventional time-depth conversion method has a difficulty in reflecting the complex stratigraphic velocity variation in the whole area, achieves conversion of the time domain seismic data volume into the depth domain seismic data volume, facilitates the actual reflection of the stratigraphic reflective interface morphology in the entire area, and provides accurate and reliable depth domain seismic data processing results for exploration and development.