The invention discloses a substitution and control method for a fault sensor in an air conditioner under refrigeration mode, which is suitable for a coil pipe sensor and a gas pipe sensor for respectively detecting the coil pipe temperature of a radiator of an indoor unit and the gas pipe temperature of an indoor-outdoor union pipe in the indoor unit of the air conditioner. When the gas pipe sensor has fault, the detecting value of the coil pipe sensor substitutes the detecting value of the gas pipe sensor by a correcting method, and participates in the control and calculation of a main control program; and when the coil pipe sensor has fault, the detecting value of the gas pipe sensor substitutes the detecting value of the coil pipe sensor by the correcting method, and participates in the control and calculation of the main control program, thereby ensuring that the unit can continuously run while reporting the error and waiting for maintenance, further avoiding the inconvenience brought to users caused by disorderly closedown and improving the service comfort of products.