Objective To explore the effect and mechanism of low molecular weight heparin calcium (LMWHC)on mouse embryo implantation. Methods A mouse pregnancy model was established and LMWC was injected intraperitoneally. The effects of LMWHC on mouse embryo implantation were then observed. Mouse trophoblasts were isolated, cultured, and treated with various concentrations of LMWHC. Transwell chambers were used to examine cell invasiveness. ELISAs, western blotting, and RT-PCR was used to detect the expression levels of matrix metalloproteinase-2 (MMP-2) and tissue inhibitor of metalloproteinase-2 (TIMP-2). Results After intraperitoneal injection of LMWHC into pregnant mice, the numbers of embryo implantations at days 6 and 9 of pregnancy were increased significantly ( P <0. 05).At 24 h after LMWHC injection at 1 × 10² , 1 × 10³ , and 1 × 10⁴ IU/ L, invading trophoblast numbers were (84. 83 ±14. 15), (162. 48 ± 25. 49), and (98. 73 ± 12. 77) respectively, significantly different from the cells without LMWHC treatment (65. 27 ± 13. 92) ( P <0. 05). The level of MMP-2 in the culture supernatant of trophoblasts was higher than that in the culture supernatant of cells without LMWHC treatment ( P < 0. 05), while the level of TIMP-2 was lower than that in cells without LMWHC treatment ( P <0. 05). Conclusions LMWHC promotes mouse embryo implantation, and its mechanism may be related to enhancement of the invasiveness of trophoblasts by affecting the expression of MMP-2 and TIMP-2.