About the embedded terminal equipment upgrade difficult problem, this paper designs a remote upgrading scheme based on STM32. The scheme study the communication flow of Ymodem protocol, and IAP technology principle and IAP function realization based on STM32, including set the initial position and the interrupt vector table, APP program area flash erase, APP program written in flash, IAP jumps to APP procedures and so on. This paper using the RS232 standard serial port realizes the communication between PC and embedded terminal equipment based on Ymodem Protocol, namely embedded terminal equipment real time updates by remote mode. Experiments show that, the design has good application value and extension value.