【Objective】To investigate associations between the functional polymorphisms of signal transducer and activator of transcription 4（STAT4）gene and unexplained recurrent spontaneous abortion（URSA）and between STAT4 protein expression and the genotypes of rs10181656 locus.【Methods】PCR-restriction fragment length polymorphism was used to genotype rs10181656 locus polymorphism in 332 URSA cases and 260 normal controls，in 86 URSA cases and 77 normal controls of which immunohistochemical technique was used to detect STAT4 protein expression.【Results】The frequencies of rs10181656 C/G were 36.45％，46.54％ in gen? otype C/C，46.99％，45.38％ in genotype C/G and 16.57％，8.08％ in genotype G/G between URSA patients and normal controls. They reached statistical difference（P < 0.05）. The carriers of rs10181656 G allele increased the risk of URSA（OR = 1.50，P < 0.05）. STAT4 protein expression in decidual tissues：①There was statistical difference in the STAT4 protein expression in decidual tissues between cases and controls（P < 0.05）. In URSA patients there was statistical difference in the STAT4 protein expression among genotype CC，CG and GG of rs10181656 locus（P < 0.05）. So was in normal controls（P < 0.05）. In genotype CC there was no difference in the STAT4 protein expression between cases and controls（P > 0.05）. Neither was In genotype CG and GG respectively （P all > 0.05）.【Conclusion】Functional polymorphisms of the rs10181656 locus could probably associate with the susceptibility of URSA via STAT4 protein expression increased by genotype G/G in maternal decidual tissue.