Abstract: By the use of low-angle laser light scattering photometer, the associateon mannerof matrix and protein in water or water acetonitrile solution was investigated. The matrices studied were 2, 5-dihydroxybenzoic acid, caf feic acid, nicotinic acid and 3-amino-4-hydroxybenzoic acid and the proteins were lysozyme and cytochrome C. The resultsdemonstrated that the apparent molecular weight and the second variel coefficient A2 insolution of 3-amino-4-hydroxybenzoic acid with lysozyme of cytochrome C were at leastthree time higher than that in the otherthree matrices solution. It means that in the solution, 3-amino-4-hydroxybenzoic acid associated very strongly with these two proteinsReferring to the effects on matrix-assisted laser desorption/ionization mass spectrometry,the above results were discussed.