The invention discloses a technological method for purifying 1,4-butanediol and co-producing tetrahydrofuran. The technological method comprises the following steps: a raw 1,4-butanediol material flow containing 2-(4-hydroxyl butoxy) tetrahydrofuran enters a 1,4-butanediol refining tower, and a 1,4-butanediol product is produced at the side line of the refining tower; and material flows rich in the 1,4-butanediol at the top and bottom of the refining tower enter a tetrahydrofuran reactor, dehydration cyclization is continuously carried out for producing the tetrahydrofuran through a palladium carried sulfonating ion exchange resin catalyst in the presence of hydrogen; after reaction, a raw tetrahydrofuran material flow enters a gas-liquid separator, a gas phase flow is reused or is discharged, and a liquid phase enters an azeotropic distillation tower; and azeotrope of tetrahydrofuran and water is obtained at the tower top and is separated to obtain the tetrahydrofuran product, liquid at the tower bottom enters a dehydration tower, and a material flow at the tower bottom returns to the tetrahydrofuran reactor. According to the technological method, the tetrahydrofuran with the high selectivity is produced while the 1,4-butanediol product with the high purity is separated out, the seperation problem of the 2-(4'-hydroxyl butoxy) tetrahydrofuran in the 1,4-butanediol product flow is solved, and the production cost is greatly reduced; and the technological method is suitable for industrial application.