Objectiveto detect polymorphism of asthma related genes. Methods Patients diagnosed asthma were divided into twogroups , one group has genetic susceptibility , the other has no such character. DNA were extracted from the peripheral blood, then TG se-quence in second intron of IL-4 was amplified by PCR, the polymorphism of that segment were then detected through 8% po]yacrylamidegel. Resultfour kinds of penotype were found in such segment. The frequency of phenotype 1 and type 2 of in test group are statisticallydifferent from that in the check group. But the other two phenotype frequencies are just the same in two groups. Conclusionthe differentfrequency of phenotype I and phenotype 2 in two groups may give us some meaning in asthma genetics.