Abstract: Concerning the license plate with a great amount of location computation and long positioning time，a fast and practical positioning system is designed.Firstly，the license plate image is preprocessed with histogram equalization，and candidate district is determined with improved Prewitt edge detection operator，Projection and Mathematical Morphology.Then，the interfered district is excluded by the feature of geometric and color.At last，positioning effects are compared under various environment.Besides that，results are provided，and the system has some value to study and socioeconomic performance.

Key words: license plate location, edge detection, Projection, Morphology

摘要： 针对车牌定位计算量大、定位时间长问题，设计了一套快速实用的定位系统。对车牌进行直方图均衡的预处理，通过改进的Prewitt边缘检测算子、投影和数学形态学方法确定候选区域队列，利用车牌的几何和颜色特征排除候选车牌区域中的干扰区域，对各种环境下定位效果进行了比较，给出了相应的实现结果，具有一定的研究价值和社会经济效益。

关键词: 车牌定位, 边缘检测, 投影法, 形态学