An image processing program with good instantaneity for gasoline direct injection spray based on Matlab/GUI was designed and the program realized visual operation interface. As gasoline is fuel with great volatile, the spray boundary of GDI image is relative obscure and SNR of the spray image is not satisfied compared with that in diesel injection. To get the accurate spray penetration, cone angle, perimeter, area and other needed parameters, the spray boundary was precisely extracted in the image processing. Noise filtering, boundary detection，morphological analysis and other related methods have been used. After the spray boundary was obtained, program to calculate spray penetration, cone angle, injection velocity and other parameters was developed to realize real-time measurement of spray parameters.