Abstract: 【Objective】To determine the sensitivity of Margarya melanioides and Cipangopaludina chinensis to pesticides used commonly in tea cultivation to explore the feasibility of Margarya melanioides and Cipangopaludina chinensis as the organisms to monitor pesticide residues in a tea garden.【Method】The lethal concentration 50（LC₅₀） values of five insecticides and one herbicide to M.melanioides and C.chinensis were determined by static bioassay tests respectively.【Result and conclusion】The LC₅₀ values of dichlorvos, fenpropathrin, abamectin, chlorpyrifos, glufosinate-ammonium and thiamethoxam to M.melanioides were 0.031 6, 0.005 2, 0.104 0,0.048 6, 14.417 1, 54.635 9 mg·kg^-1 respectively, and to C. chinensis were 1.711 2, 0.013 2, 0.917 1, 1.501 6, 108.755 3, 119.021 1 mg·kg^-1 respectively after 48 h treatment， which indicated that the sensitivity of M. melanioides to these pesticides were 54.15, 2.54, 8.82, 30.90, 7.54 and 2.18 times over C.chinensis, respectively. M.melanioides was more sensitive than C.chinensis to these six pesticides, especially to organophosphorus (dichlorvos and chlorpyrifos). The LC₅₀ values of dichlorvos, chlorpyrifos and fenpropathrin were far below the maximum residue limit (MRL), which indicated that the tested M.melanioides might have the potential to be the indicator organism to monitor pyrethroids and organophosphorus insecticide residues in tea garden．