Mountain torrent is one of major natural disasters for humans. With the development of the Internet of things, the instrumented terminals, through which the host PC could obtain the real-time water and rainfall information and could alert to a coming disaster, have been widely applied to mountain torrent warning system. In order to ensure the effectiveness of network alerting, the program in the terminals need to be updated for some specific situations, but large quantities of terminals are usually built in complex terrain and fragmented geographically, so that it is difficult and expensive to update or repair the programs. In this paper, a method of remote update, realized on the BAM-4300 hydrologic remote terminal to update the complex programs via GPRS modules, was highly reliable. Experiments show that this method is of safety and reliability, and cumbersome processes of onsite update and maintenance could be avoided.