The invention relates to an accurate positioning, welding and conveying device which comprises a power transmission mechanism, a positioning pin mechanism and a rail mechanism in connection. The power transmission mechanism comprises a rail connecting seat, a travelling gear, a driving motor, a body mounting seat, a guide wheel mounting plate and a track roller, the positioning pin mechanism comprises a linear bearing mounting seat, a linear bearing, a cylinder mounting seat, a positioning pin, a positioning pin connecting plate, a cylinder, an internal circlip, a cylinder head pressing block, a cylinder head and a positioning and mounting frame, and the rail mechanism comprises a support mounting frame, a linear guide rail, a linear guide rail shield, a rack, a shield mounting plate and a rack positioning block. The conveying device is fast and stable in running, high in positioning accuracy, small in occupied space, simple in structure, reasonable in design and widely applicable to a multi-vehicle flexible welding line of automobile automation, type exchange time can be effectively saved, positioning accuracy of a fixture is improved, product qualification rate is effectively increased, and production efficiency is greatly improved.