A
defrosting judgment method comprises the following steps that a
temperature difference starting point is selected, specifically, a
temperature difference average value is calculated, the
temperature difference variation rate is calculated, and if the sum of k1 times of temperature difference variation rates is larger than a first set threshold value or smaller than a second set threshold value, the temperature difference starting point is calculated again, otherwise whether frosting occurs or not is judged; the temperature of an
evaporator and an outdoor environment temperature are continuously collected for k2 times, and if the k2 times of temperature difference variation rates exceed the temperature difference variation rate of the set proportion and are larger than a frosting judgment threshold value, whether deforesting is needed or not is judged, otherwise the temperature difference starting point is calculated again; and the temperature of the
evaporator and the outdoor environment temperature are continuously collected for k3 times, and if the continuous k3 times of temperature difference variation rates are smaller than the standard temperature difference variation rate, it is considered that
frost layers are accumulated thickly, a
defrosting step is executed, otherwise calculation is conducted again. According to the
defrosting judgment method,
wave disturbance caused by changing
system working states can be removed, and the defrosting condition can be judged accurately.