Object To study the suitable conditions for the pac king of volatile oil in Rukang Capsule, which will inhibit the loss of volatile oil. Methods With the packing rate as index, even design method wa s applied to investigate the optimal packing conditions. Results The optimal packing conditions were found to be: volatile oil volume (mL)-cy c lodextrin (g)=1∶6, the packing process should be carried out for 120 min under 40 ℃. Conclusion The repetition rate is very good in the repeti tion experiments.