Biochar was prepared at 500℃(MX500) and 700℃ (MX700) with sawdust as raw material. The effects of initial pH of solution and the dosage of biochar on adsorption properties were studied. The adsorption characteristics and mechanism of sawdust biochar in the aqueous solution of three commonly-used pesticides: atrazine (ATR), carbendazim (CAR) and acetamiprid (ACE), were investigated using adsorption kinetics, adsorption isotherm and Fourier transform infrared spectroscopy (FTIR). The results indicate that when sawdust biochar was prepared under pyrolysis temperature of 700℃, pH of 3.0 and the dosage of biochar is 2.0 g/L, it has the best adsorption efficiency to the three pesticides. The maximum adsorption capacity of MX700 for ATR, CAR and ACE are 40.2, 50.4 and 44.9 μg/g, respectively, which is about 1.4 - 2.2 times higher than those of MX500. The results of adsorption kinetics and adsorption isotherm show that the adsorption process can be well explained by the pseudo-second-order kinetic equation, intra-particle diffusion equation and Langmuir equation. FTIR results show that sawdust biochar removes ATR, CAR and ACE from water mainly through the complexation of oxygen-containing functional groups such as phenolic hydroxyl and carboxyl groups and the aromatic ring structure. The adsorption mechanisms of sawdust biochar to pesticides including electrostatic force, hydrogen bond force and π-π bond interaction force. At the concentration of 100 μg/L the adsorption effect and mechanism of sawdust biochar for ATR, CAR and ACE are similar to that of pesticide monomers. This study indicates that sawdust biochar has great application potential as an adsorbent for the purification of water polluted by composite pesticides.