Abstract: Based on the principle of CPS3 chart system and conventional time depth conversion, a time depth conversion procedure, which takes velocity stack as its first step, has been developed for seismic data processing.The procedure was designed for an area with great lateral velocity variations, big target formation depth and only a little borehole data available.It was successfully applied to the interpretation of a 3-D data derived in the area of TSK in a north China coalfield.The procedure improved traditional time velocity conversion and the depth value of structure map produced was in accordance with mining data.