The flavor characteristic of 3-methylthiopropionaldehyde in beer and its contribution to the beer wort flavor were researched,its threshold in beer was also determined.The results indicated that the flavor of 3-methylthiopropionaldehyde was grist braised.It resembled beer wort flavor and its content is positively correlated with the beer wort flavor.Therefore,3-methylthiopropionaldehyde could manifest the wort flavor of beer.Distinctive threshold in beer was 5.0μg/L.Distillation and liquid/liquid extraction were operated on samples.Following GC/MS quantification,we could obtain its content.The correlation coefficient of 3-methylthiopropionaldehyde by external standard method was 0.9952.The precision was 4.57%.The recoveries were 83.71%~92.48%,with the limit of detection was 0.015μg/L.Different beers were analyzed with this method and the result showed a below 50μg/L content of 3-methylthiopropionaldehyde,which should be the upper limit of control standard.