The Terahertz wave has some characteristics of high penetration, low energy and fingerprint spectrum, etc., and is widely used in the detection field. Therefore, design of Terahertz wave detection optical imaging system holds substantial significance and wide application prospects. Firstly, referring to the structure of Tessar objective lens consisting of four lenses, we apply the aberration theory of paraxial optical system to establish the balance equations of aberration of the system, and give solve function and method of the initial structure parameters of the system. Then, by combining with optical design software to further correct the aberration of the system. Finally, a Terahertz wave detection optical imaging system with large aperture is designed. The optical system is composed of four coaxial refractive lenses. Its total focal length is 70 mm, F-number is 1.4, full field of view angle is 8°. The value of modulation transfer function (MTF) in the range of full field of view angle is greater than 0.32 at the Nyquist frequency of 10 lp/mm, and the root mean square (RMS) radius of the diffused spot in each field of view is less than the Airy disk radius. At last, we analyze and discuss the various tolerance types of the system. The design results show that the Terahertz wave detection optical imaging system designed in this paper has a large aperture, a simple and compact form, a light-weight structure, excellent imaging performance and simple processing, etc., which meets the design requirements, and it has important applications in the field of high-resolution detection and other fields within the Terahertz wave band.