Abstract: Three methods to determine The molecular weight of a protein electroblotted onto PVDF or NC membrane have been investigated in this paper The "Pseudo-dissolution Method"(direct method) is able to directly analyze proteins on membrane provided a good staining-destaining process and a gentle transferring strategy were carried out. The "Extraction Method" is suitable for various kinds of membranes, its reproducibility, sensitivity, and resolution are high. The"Dissolution-Precipitation Method" is the best among these methods. The quality of MALDI-TOF spectrum using this simple method is the same as The routine strategy of MALDI.