The major purpose of IC card payphone remote download processor is to provide an efficient way to update the firmware of IC card payphone. Instead of changing the Flash ROM in person, we can update firmware remotely. The design of the firmware is composed of six independent program units and each of them can be updated respectively. Basing on the modularization design of IC card payphone, remote download processor can download partial application programs and then achieve the goal of updating firmware remotely. In a word, remote download processor is an implementation of multi-thread and multiple ports serial communication. Therefore, its stability and efficiency are the two chief considerations for us to develop the system.