The invention discloses an automatic belt buckle assembling machine which comprises a machine frame, an assembling executing mechanism arranged on the machine frame, and a controller electrically connected with the assembling executing mechanism. The assembling executing mechanism comprises a torsional spring conveying mechanism arranged at one side of the machine frame, a copper pipe conveying mechanism arranged at the other side of the machine frame, a plug conveying mechanism arranged between the torsional spring conveying mechanism and the copper pipe conveying mechanism, a first assembling mechanism arranged at one side of the plug conveying mechanism and used for assembling and combining the torsional spring of a belt and a plug into a whole, a second assembling mechanism assembled behind the plug conveying mechanism and used for assembling a main buckle head of the belt, the torsional spring, a bottom piece and a copper pipe into a whole, a copper pipe assembling mechanism arranged at the side edge of the second assembling mechanism, connected with the copper pipe conveying mechanism and used for installing a copper pipe, and a third assembling mechanism arranged above the first assembling mechanism and used for assembling rivets. The machine is high in automatic degree, capable of effectively improving the production efficiency and lowering the labor cost and easy to operate.