The present invention discloses compounds of formula (I), their optical isomers or pharmaceutically acceptable salts thereof, their preparation and uses thereof, wherein the definitions of R1, R2, R3 and R4 are shown in the description. These compounds are optical isomers or racemic mixtures. After these compounds are uptaken, they are metabolically transformated in vivo into 1-[2-dimethylamino-1-(4-hydroxyphenyl)-ethyl]-cyclohexanol that has neuropharmacological activity, by interrupting reuptake of 5-hydroxytryptamine (5-HT) and/or norepinephrine (NA), which is used for treating diseases associated with central nerve system, such as depression, etc.
