The invention provides an indoline compound of 1-(3-substituted benzoyl alkoxypropyl)-5-(2-nitrylpropyl)-7-cyanophoric indoline and a preparation method thereof. The indoline compound can be used as an intermediate compound and is used for synthesizing silodosin. The indoline compound uses substituted phenylformic acid as a raw material, is prepared by multiple-step reaction, has high yield and is easy to industrially produce.