Abstract: Carboxymethyl-chitosan (CMC) was combined with modified bentonite,and used as the carrier of herbicide atrazine to prepare granular formulations with controlled release function,so as to slower its release,reduce its leaching,enhance its efficacy and control its pollution.The release experiments in water were used to investigate the influence of formulations on the release rate of atrazine.The release mechanism was discussed by using a semi-empirical model.The experiments on a thin soil layer were used to investigate the effect of composite carrier on reducing the leaching of atrazine.The results showed that,the time taken for 50% of atrazine released ( t 50) was prolonged to more than 700 h by using the composite carrier,which is 2 times longer than using CMC alone as the carrier.The release process was dominated by the Fickian diffusion,and the cumulative percentage of atrazine leached was only 6.0% after 9 times of rinsing with water,in this way the pollution of atrazine to groundwater may be greatly reduced.