A method for preparing high-content conjugated linoleic acid (CLA) through purification of vegetable oil includes alcoholysis, purification and isomerization of vegetable oil. Alcoholysis is for preparing corresponding methyl ester or ethyl ester with glyceride; purification of methyl ester or ethyl ester is for obtaining methyl linoleate or ethyl linoleate of content over 85% through silver-based silica gel column chromatography; high-content CLA is obtained after alkali-catalyzed conjugation of methyl linoleate or ethyl linoleate, and CLA products are prepared as needed. This invention changes the status quo of preparing high-content CLA with safflower oil alone, expands sources of CLA, and develops an efficient technology for separation and purification of linoleic acid. The CLA obtained is of high purity and meets applications in pharmaceutical, health care products and other industries.