The invention discloses a closed-loop hot galvanizing 
production line and a control method. The closed-loop hot galvanizing 
production line comprises a preplating device (1), a galvanizing device (2),a postplating device (3), a travelling rail unit and an 
electronic control unit. The device (1) used before galvanizing comprises a 
degreasing pool (12), a 
water washing pool I (13), a 
zinc removal 
pool (14), an acid cleaning pool (15), a reduction pool (16), a 
water washing pool II (17), a spraying pool (18), an addition agent pool (19) and a 
drying chamber (110), wherein the 
degreasing pool (12), the 
water washing pool I (13), the 
zinc removal pool (14), the acid cleaning pool (15), the reduction pool (16), the water washing pool II (17), the spraying pool (18), the addition agent pool (19)and the 
drying chamber (110) are connected with the interior of a chamber (11) used before galvanizing in sequence. The postplating device (3) and the galvanizing device (2) are perpendicularly arranged. The travelling rail unit comprises a travelling rail device (4) and a travelling rail electronic 
control circuit, wherein the travelling rail device (4) is located above the preplating device (1), the galvanizing device (2) and the postplating device (3). By the adoption of the closed-loop hot galvanizing 
production line and the control method, the content of iron entering the hot galvanizingworking procedure can be effectively reduced, the waste of liquid 
zinc is reduced, the frequency of treatment of dangerous waste iron mud is reduced, the purpose that the surface quality of a galvanized part is better is achieved, and the production efficiency is improved.