In order to increase the valid view of field, make it easy for using, and save cost, it's necessary to improve the performance of the existing rigid endoscope. Firstly, the development status and main problems of rigid endoscopes at home and abroad are analyzed. And the design requirement is proposed by comparing related product. Next, a design method of 30° viewing angle rigid endoscope is proposed. Then, on the basis of the analysis of the current steering system structure of all kinds of rigid endoscope on the market, a method of designing the 30° viewing angle endoscope with total reflection prism is proposed. Finally, the tolerance analysis and image quality evaluation are carried out according to the corresponding standard. The design results show that the total length of the designed endoscope is 365 mm. The diameter is less than 6 mm. The angle of the field of view is ±40°. And the object space resolution is 12 lp/mm, which is close to the diffraction limit. The energy distribution is uniform as well. Considering the processing and assembly error, the results show that the image quality can still meet the user needs after the tolerance analysis. The design results can basically meet the actual use needs and the design requirements, which have engineering application significance for the localization of high quality medical rigid endoscope.