Due to the limitation of the contact measurement, a non-contact measure object dimension based on the virtual instrument was designed. The object images were captured by CCD. Through the de-nosing, image segmentation, edge detection, the system computed the size of the object. Finally, the system read, write, storage and display the measurement data by use of the database systems interact. The experimental results show that: the system meet the requirements of high precision, avoid human error and reduce the testing cost and suitable for the harmful industrial environmental.