Time-dependent and pH-sensitive polymers are applied to be coating materials in certain level to achieve colonic targeted delivery.In this study, drug release from coated pellets containing total alkaloids of sophora alopecuroides were adjusted by coated with time-dependent and pH-sensitive polymers in different coating order.Free films of Eudragit S100 and Eudragit S100 coated with Eudragit RS30D were prepared by immersing methods and the pellets were prepared by extrusion-spheronization then coated with Eudragit RS30D and Eudragit S100 in different coating order.Results showed that as the coating level of Eudragit RS30D increase, the rate of swelling and dissolve of free films decrease, as shown in Fig.1.0.10355±0.01040 g of free film of Eudragit S100 (A) reached the mixture swelling within 7 h and dissolved completely within 18 h, while free film of B and C, which containing 0.06883±0.003565 g and 0.11385±0.000525 g of Eudragit S100 and coated with Eudragit RS30D in different level, respectively, the mixture swelling time of B and C retarded to 20 h and 22 h respectively and did not dissolved completely within 52 h.the results indicated that the time of free films reach mixture swelling and dissolved completely is related to the effect of Eudragit RS30D film, and results of drug release study (Fig.2) confirmed that pellet core coated with Eudragit S100 as inner layer and Eudragit RS30D as outer layer required a lower coating level than that coated in opposite order.Formulation F4, coated with 12.8% of Eudragit S100 as inner layer and 14.8% of Eudragit RS30D as outer layer, shown colonic drug release.No drug release within 2 h and no more than 9% was released within 5 h, all drug released within 24 h, while F2, coated with 12.8% of Eudragit RS30D as inner layer and 21% of Eudragit S100 as outer layer, up to 42% of the drug release within 5 h.Experiments of swelling and dissolve of free film and drug release confirmed that pellets coated with pH-sensitive polymer as inner layer required lower coating level and achieved colonic drug release than that coated them as outer layer.