In some high-cost industrial field, in order to make image processing technology make up for deficiencies in existing control methods and also have a high economy, this paper presents a smart elevator door control system based on image processing technology. Select atmega32 as the main control chip and ov7620 as image acquisition chip. Design plans to resolve the defects of 8-bit microcontroller in the course of image processing. According to the feature of image pixels, we use Semi-Neighborhood Averaging Algorithm combined with Background Difference Method for moving objects identifying. Experimental results show that the system's real-time performance and adaptability accord with all basic requirements. It will bring considerable economic benefit and great practical value.