Abstract: Objective: To investigate the surgical principle of chronic sinusitis.Methods: he effect of three surgical procedures was compared.Transmaxillary sinus ethmoidectomy(Lima's operation) was performed on 38 cases,endoscopic sinus surgery(ESS) on 31 cases and endoscopic plus Caldwell-Luc sinus surgery on 27 cases.Results: All the cases were followed up from 12 months to 24 months postoperatively.In the Lima's operation group,36.84% of the patients were cured,52.63% improved and 10.53% had no response;in the ESS group,51.61% of the patients were cured,38.71% improved and 9.68% had no response;in the endoscopic plus Caldwell-Luc sinus surgery group,77.78% of the patients were cured,14.81% improved and 7.41% failed to respond.The difference was significant.Conclusions: The approach of endoscopic plus Caldwell-Luc sinus surgery can remove the focus completely,clear the drainage thoroughly and resume the functions of nose and sinuses better.