Using pig manure as raw material, biochar was prepared at different temperatures and ash removal treatment was carried out. The interaction between biochar and carbaryl at different treatment temperatures and ash content was studied. The biochar prepared from pig manure contains inorganic minerals, indeterminate organic matter and crystalline aromatic carbon, and as the treatment temperature increases, the ash content increases and the BET specific surface area increases. The adsorption of carbaryl by biochar is non-linear, and the isotherm conforms to the Freundlich equation, and the nonlinearity increases as the temperature of biochar preparation increases. After the ash removal of biochar, the adsorption effect is greatly enhanced, indicating that the recombination of organic carbon and inorganic components causes the loss of some of its adsorption sites. The adsorption of carbaryl by biochar is composed of lipophilic distribution and special force. With the difference of biochar and the concentration of carbaryl, the adsorption mechanism changes. Biochar can increase the pH of the solution. The pH increases with the amount of biochar and the treatment temperature. The minerals contained in biochar have a catalytic effect on the hydrolysis of carbaryl, and the rate and degree of hydrolysis are positively correlated with the ash content of biochar.