Objective To investigate biomechanical properties of the complete mandibular subperiosteal implant under four different bite loads, and provide some references for the personalized implant design in clinical cases. Methods Based on the three-dimensional model of human mandible, two kinds of matching complete mandibular subperiosteal implants, meshy base (implant 1) and zonary base (implant 2), were established, respectively. Stress distributions of both the two implants under four different bite loads were calculated and compared. Results The maximum stress of implant 1 was 230.42 MPa under the load Ⅳ and that of implant 2 was 311.11 MPa under the load Ⅰ. The stress distributions and maximum stress showed that the implant with meshy base had better resistance to the vertical loads, while the implant with zonary base had better resistance to the horizontal loads. Conclusions Rational arrangement for the number of posts and the distance between posts can effectively control the stress of implants. Posts should be placed in a vertical direction with the alveolar bone to avoid amplifying the horizontal component. In addition, posts should be well bounded to the bases, so that the stress on the bottom of posts won’t be at a high level. The complete denture should be guaranteed to contact at several spots during centric, protrusive and lateral bites to keep occlusion balance and decrease the maximum tensile stress on the contact surface.