The alginate (SA) composite microgel beads loaded the emamectin benzoate were prepared with calcium chloride (CaCl2) and chitosan (CS) as cross-linking agents, bentonite (BT) as an adsorbent. Furthermore, the Box-Behnken design was used to build the model and to analyze the effects of the mass fraction of sodium alginate (1.00~3.00 wt.%), the mass fraction of bentonite (1.00~5.00 wt.%), the concentration of calcium chloride (0.10~0.40 mol/L) and the fraction concentration of chitosan (0.50~1.50 wt.%) on the respond value, regarding the ratio of drug loading rate (DLR) to equilibrium swelling ratio (ESR) as the response value (UR，UR=DLR/ESR). Experimental results showed the relationship between the response value and four independent variables were in line with the quadratic model. That mathematical regression model had good predictability and the optimal conditions within the experimental ranges for the response value were forecasted to be 2.39 wt.% sodium alginate, 2.81 wt.% bentonite, 0.24 mol/L calcium chloride and 0.71 wt.% chitosan. Under these optimal conditions, the average value of the actual response value in three replicated experiments is 3.5509%, which is not significantly different from the value of 3.5836% predicted by the model. In addition, the composite beads prepared under the optimal conditions have encapsulation efficiency of 2.11%, drug loading rate of 98.31% and good sustained-release properties.