Abstract: Background　Silicon nitride (Si3N4) is a promising bioceramic material for dental applications, and digital light processing (DLP) is an advanced 3D printing (additive manufacturing) technology with high fabrication precision. However, there is a paucity of systematic investigations on DLP-fabricated porous Si3N4 dental implants with Diamond-type triply periodic minimal surfaces (TPMS) architecture.Objective　The aim of this study was to fabricate porous Si3N4 ceramics with Diamond-type TPMS architecture and a pore size gradient ranging from 300 to 600 μm via DLP technology, to characterize their microstructure and mechanical properties, and to identify the optimal pore size parameters suitable for dental implant applications. Methods Based on the topological characteristics of Diamond-type TPMS structure, three-dimensional models with four different pore sizes (300, 400, 500, and 600 μm) were designed with a fixed unit cell size. The fluctuation of total porosity among each group was strictly controlled within 5% to establish a single-factor experimental system with pore size as the sole variable. Green bodies were printed via DLP technology and sintered at high temperature to prepare specimens, with 5 - 6 replicate specimens set for each group. The phase composition and microstructure of the materials were characterized by X-ray diffractometer (XRD) and scanning electron microscope (SEM). Total porosity was measured by the Archimedes method. The flexural strength and elastic modulus of the specimens were tested using a universal mechanical testing machine in accordance with ISO 14704-2016 and GB/T 10700-2006 standards. One-way analysis of variance (ANOVA) was used for statistical comparison of data among groups.Results　 The main crystalline phase of the as-prepared samples was β -Si3N4, with an intact macrostructure and a three-dimensionally interconnected pore network. As the designed pore size increased, the total porosity of the samples increased in a gradient manner from 45.04% to 50.06%, the flexural strength decreased monotonically from 110.69 ± 1.25 MPa to 74.47 ± 1.05 MPa, and the elastic modulus exhibited a stepwise non-linear increase accompanied by minor fluctuations throughout the variation. There were extremely significant statistical differences in all core mechanical parameters among the groups (P＜0.001). Notably, the group with a designed pore size of 300 μm presented the optimal combination of mechanical properties, with the highest flexural strength (110.69 ± 1.25 MPa) and a low elastic modulus of 13.45 ± 0.20 GPa, which was highly consistent with the mechanical parameter range of human mandibular cortical bone. Conclusion Tailoring the pore size parameters of Diamond-type TPMS structure can effectively and synergistically regulate the pore characteristics and mechanical response properties of porous Si3N4 ceramics. The 300 μm pore size structure achieves the optimal balance between high strength and low modulus, with excellent mechanical compatibility with bone tissue. It provides core experimental basis and data support for the optimal design of the porous surface structure of highperformance "dense core-porous surface" gradient Si3N4 dental implants.