Covalent organic framework (COF) materials with regular microstructures are important for structuring stable pore structures and ensuring the uniform arrangement of active sites. Furthermore, the crystallinity of the COF backbone usually shows a great influence on the coordinated microenvironments of the loaded active sites. Therefore, the investigation of crystallinity and bond environment on single atoms for HER is of great importance. Herein, we synthesized TTB-COF with different crystallinities loaded with Pt atoms to reveal their influence on HER activities. The optimized Pt@TTB-COF with high crystallinity and homogenously distributed Pt single atoms exhibited excellent HER performance with an overpotential of 5 mV to reach the current density of 10 mA cm⁻², high turnover frequency (TOF) value of 5.43 H₂ S⁻¹ at the overpotential of 50 mV, and constant stability. This work not only provides a simple method for synthesizing covalent organic framework materials with uniform morphology but also provides a new light for the construction of a new generation of highly efficient and stable HER electrocatalysts.