The Taiji program aims to achieve space gravitational wave interferometry measurement through quasi-equilateral triangle satellite groups and explore major phenomena in the universe. We detail the design and wavefront test of the space gravitational wave detection telescope, which is one of the core payloads of the Taiji program. It features an all-glass-ceramics structure aiming for an optical path stability of ≤1pm/Hz1/2. The telescope, with a 400-mm aperture and an off-axis reflective optical system, comprises two large glass-ceramics components, easing assembly and connectivity challenges. The weight of the telescope is 19 kg, which meets the ≤20kg system requirement. Ground wavefront test methods were optimized using a “hanging-ear” support approach. Under 1 g gravity, the wavefront error of the system is 0.018λ [root mean square (RMS), λ=1064nm], and considering processing, assembly, and in-orbit temperature conditions, the space environment system wavefront distortion RMS is ∼0.045λ (λ/22), meeting the RMS ≤λ/20 requirement. This design and testing method lay the groundwork for subsequent assembly and in-orbit application of the telescope, providing key technical support for the implementation of the Taiji program.