Ink-jet printer for jet printing on surface of cylindrical product and use method

The invention provides an ink-jet printer for jet printing on the surface of a cylindrical product and a using method, the ink-jet printer comprises an upper rack, the upper rack is provided with an ink-jet head capable of doing reciprocating motion, the upper rack is further provided with a rotation driving module and a product positioning mechanism, the rotation driving module comprises a transmission rod driven by a rotation motor, and the transmission rod is connected with the ink-jet head. The product positioning mechanism comprises a rear end positioning block and a front end positioning air cylinder, the rear end positioning block and the front end positioning air cylinder are located at the two ends of the transmission rod respectively, a lower rack is arranged below the transmission rod, and a plurality of jacking assemblies are arranged on the lower rack. The jacking assembly comprises a jacking air cylinder, a supporting spring set and a driven wheel set which are sequentially connected from bottom