The present invention provides a compound represented by formula I, wherein R is a halogen element or a C1-C6 alkyl group. The compound has S1 P1 receptor agonist activity and selective specificity and has obviously-shortened half-life in-vivo, and therefore the compound is a high-quality second-generation S1P1 receptor agonist. The present invention also provides a use of the compound in preparing medicine for treating diseases or symptoms mediated by an S1P1 receptor, a pharmaceutical composition comprising the compound, and uses of the compound and the pharmaceutical composition in treating diseases or symptoms mediated by the S1 P1 receptor.