Objective To explore the regulation of mammalian embryo implantation, we investigated the expression of Lysozyme 1 ( LYZ1 ) in normal hatching murine blastocysts and dormant embryos before and after superovulation. Methods Normal hatched blastocysts were obtained from day 5 pregnant mice, while dormant embryos were collected from delayed implantation models on day 8. LYZ1 protein expression in the embryos was detected by immunofluorescence and western blot. Results LYZ1 protein was expressed in both hatching blastocysts and dormant embryos before and after superovulation, where it was mainly concentrated in the inner cell mass. LYZ1 was rarely distributed in trophoblasts or in their cytoplasm. Compared with untreated mice, LYZ1 protein expression in superovulation embryos was significantly upregulated; moreover, LYZ1 protein expression in the dormancy model was significantly upregulated. Conclusions LYZ1 protein was expressed in the inner cell mass of embryos, where it may be involved in regulating early development. The high LYZ1 protein expression in dormant embryos after superovulation indicated that LYZ1 protein is upregulated in embryos experiencing adverse environmental conditions, such as the dual effects of dormancy and superovulation.