The invention relates to the technical field of repairing equipments for hydraulic engineering canal slopes, in particular to an upright counterweight lightweight mobile cofferdam. The upright counterweight lightweight mobile cofferdam comprises a main frame and a water retaining panel, wherein a support plate is fixed between a cross beam and a side beam, studs are vertically mounted on the support plate and respectively extend outwardly, counterweight clamping slots are formed in adjacent studs, a plurality of independent counterweight blocks are hung in each counterweight clamping slot, positioning columns are arranged on two sides of each counterweight block, sliding vertical grooves are formed in both sides of each counterweight clamping slot, a limit groove is formed in the side wall, close to the water retaining panel, in each sliding vertical groove, the positioning columns can slide down along the sliding vertical grooves and are clamped in the limit grooves, bolt holes are formed on the front sides of the counterweight clamping slots, and the inner ends of fixes bolts penetrate through the bolt holes to be propped against the counterweight blocks; the rear vertical surface of the main frame and the outer lateral side of a side frame are wading walls, light water retaining panels are mounted on the wading walls, the inner sides of the water retaining panels surround waterproof working cavities, and skirt-type waterproof rubber pads are mounted on the lower edges of the water retaining panels. The upright counterweight lightweight mobile cofferdam disclosed by the invention can be quickly mounted and disassembled, is adjustable in weight of counterweight bodies and can adapt to various working conditions.