The belt deviation was one of the indicators that measure the belt scale performance. The belt deviation detection system based on Field Programmable Gate Array and Microcontroller Unit (FPGA+MCU) was presented by aiming at the problem of belt deviation. The phototransistor array as sensing element was adopted by the system, and FPGA was used as the core of signal acquisition and processing, and communicated with the host computer, whose acquisition software was developed by using Visual Basic (VB), through MCU. The experimental results show that the system can effectively realize real-time accurate detection of the belt deviation, and has a good stability.