Abstract: In order to clarify the degradation activity of edible fungus liquid culture on pesticide pollutants, the degradation dynamics of four pesticides including dimethoate, acetamiprid, lambda-cyhalothrin and carbendazim in the liquid medium where Pleurotus ostreatus mycelia were cultured were determined using liquid chromatography-tandem mass spectrometry (LC-MS/MS) and ultra high performance liquid chromatography (UPLC-PDA). The results showed that the degradation dynamics of four pesticides in the liquid medium of mycelia followed the first-order kinetic model. And the degradation half-lives of lambda-cyhalothrin, carbendazim, dimethoate, and acetamiprid were 2.93, 4.38, 11.83 and 14.01 d, respectively. The degradation rate ranked from high to low as lambda-cyhalothrin > carbendazim > dimethoate > acetamiprid. After the liquid media was sterilized, the laccase activity in the culture medium disappeared, and the degradation rates of pesticides decreased accordingly. At 1 h and 4 h, the higher the concentration of crude enzyme solution, the greater the degradation rate of pesticides. The degradation rates of four pesticides had positive correlation with laccase activities in liquid media by ExpDec1 function analysis. It was preliminarily revealed in this study that four pesticides could be degraded and laccase played an important role. The study will provide technical support for the development of Pleurotus ostreatus for reducing pesticide residues.