A low-pressure circulation barrel structural style of an adapted liquid pump in a senior refrigeration air-conditioning system unit is characterized in that at least an umbrella-shaped block separating sheet (9) and a splash proof net (10) are arranged inside a barrel body (4), the umbrella-shaped block separating sheet (9) is positioned on the top portion or the upper portion of the inside of the barrel body (4), the umbrella-shaped block separating sheet (9) cuts through a linear connection line between a nozzle of a muffler (6) and a nozzle of an exhaust tube (5), the gas-liquid separation action of a returned refrigerant is conducted in accordance with different proportions, the splash proof net (10) is arranged between a nozzle of a liquid supply pipe (P) and the nozzle of the muffler (6) and is used for blocking the refrigerant, and the splash proof net (10) can reduce the splashing strength of the expansion liquid refrigerant sprayed by the liquid supply pipe (P) and the splashing strength of a liquid surface (1) of the refrigerant which is subjected to impact. By the aid of the above technical schemes, a knock phenomenon that a liquid is sucked to a compressor (3) under the condition that the volume of a low-pressure refrigeration circulation barrel is reduced greatly is avoided. Conditions are provided for the compact structural style of an air-conditioning unit.