The invention provides a technology for treating dilute hydrochloric acid waste liquid generated in the production process of an ADC (azodicarbonamide) foaming agent. The technology is characterized in that a pressure-swing distillation desorption process is used for separating about 10% of dilute hydrochloric acid generated by using chlorine for oxidizing biurea in the production process of the ADC foaming agent; the dilute hydrochloric acid waste liquid enters the middle upper part of a pressure reduction tower, water is distilled off from the top of the pressure reduction tower, and hydrogen chloride gas is desorbed from the top of a pressing tower; the mass percent of the water distilled off from the top of the pressure reduction tower is greater than 99.99%, the COD (Chemical Oxygen Demand) content is less than 100mg/L, the nitrogen content is less than 100mg/L, and the water can be reused in the ADC production process; the mass percent of the hydrogen chloride desorbed from the top of the pressing tower is greater than 99.99%. The dilute hydrochloric acid waste liquid generated in the production process of the ADC foaming agent is recycled through pressure-swing distillation desorption operation, so that the treatment cost of the dilute hydrochloric acid waste liquid is reduced, and meanwhile, the damage on environments in the treatment process is also reduced.