Abstract: Objective :To study the expression of Simian virus 40(SY40), BK virus(BKY) and JC virus (JCV) in human brain tumor. Methods :Polymerase chain reaction was used to detect SY40, BKY and JCV DNA sequences from 23 samples of astrocytoma, 19 of oligodendroglioma, 18 of ependymoma, 12 of choroids plexuspapillomas, 11 of menigioma and 12 of normal brain tissues. Results :SY40, BKY and JCV were detected in human brain tumors and those positive rates were 56.6Y, 53.0Y and 14.5Y, respectively. The positive rates of SY40, BKY and JCY, in the normal brain tissues, were 8.3Y, 8.3Y and 16.7Y, respectively. The positive rate of SY40 was obviously higher in human brain tumors than that in normal brain tissues (P<0.01). There were significantly different expression rate of SY40 between any one of 5 type brain tumors and normal brain tissues (P<0.01). The positive rate of BKY was obviously higher in human brain tumors than that in normal brain tissues (P<0.01). There were significantly different expression rate of BKY between any one of 5 type brain tumors and normal brain tissues (P<0.05). There was not significantly difference in expression rate of JCY between brain tumors and normal brain tissues. The expression of SY40 was associated with of BKY. Conclusion :SY40 and BKY play a role in human brain tumor.