The invention relates to a processing method for improving the strength of polyurethane filaments. The processing method comprises the following steps of first dissolving polyvinyl alcohol in water, preparing size under a certain condition, then performing pre-drawing on elastic polyurethane filaments, dipping the polyurethane filaments in a size vat for dipping, performing wet-heat processing, passing through a compression roller and then braking, curing polyvinyl alcohol to form a film, and putting the polyurethane filaments in water for washing, thereby obtaining the strength-improved polyurethane filaments. The wet-heat processing method is simple to operate, low in raw material cost, and short in processing time consumed, the elastic polyurethane filaments are processed on a common slasher, and meanwhile, the bad influence on subsequent processing, caused by non-uniform tension due to non-uniform polyurethane filament elasticity and elasticity loss, is improved.