The invention discloses a pet urine pad waste collecting device based on pressure detection and an operation method thereof, belonging to the technical field of production equipment. Aiming to solve problems of no prompt after a collecting pot is full and needs of personnel concerns in the prior art, the pet urine pad waste collecting device comprises a collecting pot arranged below a rejection unit of a pet urine pad production line, a sensing frame arranged under the collecting pot, a pressure sensor arranged between the sensing frame and the collecting pot, a control module arranged on the sensing frame, and an alarm module arranged on the sensing frame, wherein the pressure sensor and the alarm module are respectively connected with the control module through guide lines. The pet urine pad waste collecting device provided by the invention has the beneficial effects of convenience and reliability, greatly improves the reliability of collecting waste products, and effectively enhances the production efficiency of enterprises.