Objective: To investigate the role and significance of patally expressed gene 10 (PEG10) in deciduas of normal pregnant women. Methods: Sixty deciduas tissue from pregnant 6 to 11 weeks were divided into six groups and in each group ten samples were done every gestational week. The expression and distribution of PEG10 in deciduas were examined by RT-PCR, hybridization in situ, West Blot and laser scanning confocal microscopy. Results: The PEG10 mRNA and protein were expressed in deciduas tissue from pregnant 6 to 11 weeks. Among them, the expression of PEG10 showed a gradual increase as the pregnancy weeks increased. In RT-PCR, the PEG10 expression was lower at pregnant 6th week (0.6743+0.114), from pregnant 7 to 8 weeks, the expression was increased gradually (7th week 0.7349±0.0083) and reached the pinnacle at 8th week (0.7354±0.0074). And then the pinnacle began to descend (9th week 0.6340±0.0084, 10th week 0.5901±0.0089 and 11th week 0.5261±0.0112). There was a significant difference in the expression of PEG10 from pregnant 6 to 11 weeks except 7th week and 8th week. This expression characteristic was demonstrated by hybridization in situ. The similar conclusion was proved by West Blot and laser scanning confocal microscopy. Conclusion: Expression of PEG10 may play an important role in early pregnancy.