An expansion valve control method for a multi-connection air conditioning system, the multi-connection air conditioning system comprising an outdoor unit and a plurality of indoor units (1; 2; 3) connected to the outdoor unit, each of the indoor units (1; 2; 3) being connected to the outdoor unit through a first pipeline and a second pipeline, one of the first pipeline and the second pipeline being a refrigerant inflow pipeline, and the other of the first pipeline and the second pipeline being a refrigerant outflow pipeline, wherein the expansion valve control method comprises: obtaining an indoor temperature of an environment in which the indoor unit (1; 2; 3) is located; obtaining a temperature of the first pipeline of the indoor unit (1; 2; 3) and a temperature of the second pipeline of the indoor unit (1; 2; 3) when the indoor unit (1; 2; 3) is in a turned-off state; and determining a leakage condition of an expansion valve of the indoor unit (1; 2; 3) according to the indoor temperature of the environment in which the indoor unit (1; 2; 3) is located, the temperature of the first pipeline of the indoor unit (1; 2; 3), and the temperature of the second pipeline of the indoor unit (1; 2; 3), characterized in that when the indoor unit (1; 2; 3) is in a heating mode, the step of "determining the leakage condition of the expansion valve of the indoor unit (1; 2; 3) according to the indoor temperature of the environment in which the indoor unit (1; 2; 3) is located, the temperature of the first pipeline of the indoor unit (1; 2; 3), and the temperature of the second pipeline of the indoor unit (1; 2; 3)" specifically comprises: determining the leakage condition of the expansion valve of the indoor unit (1; 2; 3) according to a difference between the temperature of the first pipeline of the indoor unit (1; 2; 3) and the temperature of the second pipeline of the indoor unit (1; 2; 3), and a difference between the temperature of the second pipeline of the indoor unit (1; 2; 3) and the indoor temperature of the environment in which the indoor unit (1; 2; 3) is located. obtaining an indoor temperature of an environment in which the indoor unit (1; 2; 3) is located; obtaining a temperature of the first pipeline of the indoor unit (1; 2; 3) and a temperature of the second pipeline of the indoor unit (1; 2; 3) when the indoor unit (1; 2; 3) is in a turned-off state; and determining a leakage condition of an expansion valve of the indoor unit (1; 2; 3) according to the indoor temperature of the environment in which the indoor unit (1; 2; 3) is located, the temperature of the first pipeline of the indoor unit (1; 2; 3), and the temperature of the second pipeline of the indoor unit (1; 2; 3), characterized in that when the indoor unit (1; 2; 3) is in a heating mode, the step of "determining the leakage condition of the expansion valve of the indoor unit (1; 2; 3) according to the indoor temperature of the environment in which the indoor unit (1; 2; 3) is located, the temperature of the first pipeline of the indoor unit (1; 2; 3), and the temperature of the second pipeline of the indoor unit (1; 2; 3)" specifically comprises: determining the leakage condition of the expansion valve of the indoor unit (1; 2; 3) according to a difference between the temperature of the first pipeline of the indoor unit (1; 2; 3) and the temperature of the second pipeline of the indoor unit (1; 2; 3), and a difference between the temperature of the second pipeline of the indoor unit (1; 2; 3) and the indoor temperature of the environment in which the indoor unit (1; 2; 3) is located.