Abstract： Free ascent is the only way of decompression in the course of free ascent escape. When one is under high pressure, the ascent rate, the time required for the equalization of pressure are most important factors for the success of an escape. In our study, model analyses were made on the ascent of the escapee wearing the MK10 immersion suit by using mathematical methods and consulting empirical data derived from experimental results about water current. Then, ascent rate, acceleration and the time required for the equalization of pressure were calculated, which could be used for reference in the study of the ascent rule of the escapee wearing the MK10 immersion suit.