The invention discloses a disassembly-preventing connection pipe nut which comprises a connection pipe nut body, a unidirectional rotation structure and an auxiliary nut, wherein the connection pipe nut body is of a cylinder structure with a tapped blind hole in one end; the unidirectional rotation structure is arranged at the outer part of the connection pipe nut body in a sleeving manner; the auxiliary nut is arranged at the outer part of the unidirectional rotation structure in a sleeving manner. When a tightening torque is applied to the auxiliary nut, the auxiliary nut transfers the torque to the connection pipe nut body through the unidirectional rotation structure. When an unscrewing torque is applied to the auxiliary nut, the auxiliary nut rotates around the connection pipe nut body. The invention further discloses a disassembly-preventing connection pipe nut assembly, an air conditioner and a method for preventing disassembly for the connection pipe nut. The refrigerant leakage caused after the conventional pipe joint and the connection pipe nut are disassembled can be effectively avoided.