OBJECTIVE: To optimize the extraction process of oil in Laggera pterodonta (DC.) Benth by orthogonal design L9(34) and then analyze chem. constitutes in the Laggera pterodonta (DC.) Benth oil. METHODS: The experiment was performed with the extraction amount of volatile oil as the index, and the volume of water, the time of immersion, the time of extraction as affecting factors. GC-MS method was used to anal. chem. constitutes in the Laggera pterodonta (DC.) Benth oil. RESULTS: Optimized extraction process was as follows: Laggera pterodonta (DC.) Benth was soaked in 10 times of water for 2 h, and then distilled for 8 h. Twenty compounds were separated from the Laggera pterodonta (DC.) Benth oil and were identified. CONCLUSION: The method is stable and practicable. α-Copaene, β-selinene and 1,2,3,4,4a,5,6,7-octahydro-4a,8-dimethyl-α-methylene-2-naphthalene acetic acid were the main compounds of Laggera pterodonta (DC.) Benth oil, and the amount of the three compounds can attain 34.63%.