As an important subject area, image processing has a wide range of applications, such as military, scientific research and our daily life, etc. However, the disadvantage of existing image processing software makes it impossible to meet the needs of the public. The paper designs an image processing software that can run on Windows system. It takes C# as the programming language and uses Visual Studio as the development environment. The image processing assistant realizes the basic processing of the image such as image cropping and zooming, color filtering and reversing, the adjustment of transparency and contrast, etc. Results of test show that the function and performance of the image processing assistant meet the expected requirements, and can meet the daily needs of users.