In this paper, we report on the development of a forensic discrimination method for malathion formulations using the composition of organic solvents and poly (oxyethylene) surfactants contained in them. The composition of the organic solvents and the surfactants were analyzed by head-space gas chromatography mass spectrometry and matrix-assisted laser desorption ionization mass spectrometry, respectively. From examination of the solvents, 10 formulations analyzed in this study were classified into 3 groups, and from examination of the surfactants, the 10 formulations were classified into 4 groups. Finally, by combining the both results, we succeeded in classifying them into 7 groups. The result of this discrimination was consistent when those formulations were mixed with beverage samples or food samples. This method was proved to have high robustness over degradation, volatilization, or interference by matrices, which is required for the forensic discrimination of pesticide formulations.