The invention discloses an auxiliary navigation method, system and device for water-surface monitoring platform ranging by a deep-sea vehicle. The method comprises the following steps: acquiring longitude and latitude and time information of a water-surface monitoring platform; issuing the information to the deep-sea vehicle; decoding communication information to acquire the longitude and latitudeand time when the water-surface monitoring platform transmits the communication information; acquiring the time of receiving the communication information by the deep-sea vehicle; obtaining propagation delay according to the time of transmitting the communication information and the time of receiving the communication information; acquiring a sound velocity section of the deep-sea vehicle and thedeep-vehicle vehicle depth; constructing intrinsic sound ray according to the sound velocity section, the deep-sea vehicle depth and the propagation delay; obtaining the horizontal distance of the water-surface monitoring platform and the deep-sea vehicle according to the intrinsic sound ray and the deep-sea vehicle depth; acquiring inertia navigation information of the deep-sea vehicle; and performing fusion correction on the longitude and latitude information, the horizontal distance and the inertia navigation information to obtain combined navigation information. The navigation error can be modified, and the navigation precision is improved.