Abstract: A 4-month male infant presented with erythema for 1 month. He was misdiagnosed as diaper dermatitis with ineffective treatment. Laboratory tests of the infant showed positive for TPPA and anti-treponema IgM, TRUST titer was 1∶512. The parents had no lesions and the laboratory tests of parents showed positive for TPPA and the TRUST titers of the mother and father were 1∶32 and 1∶64 respectively. The mother did not receive perinatal health care during pregnancy and had no history of syphilis. The syphilis antibody of the mother detected during giving birth was positive, but no syphilis antibody test was performed for infant. Early congenital syphilis symptoms has no characteristics and easily to be misdiagnosed, doctors should pay attention to the patients with suspected syphilis and the syphilis antibody detection should be given.