A defrosting control method for a heat pump system, comprising: setting an outdoor temperature preset value, a preset constant value and an expected defrosting time; initializing a first default parameter TM n indicative of the running time of the heat pump when an outdoor temperature is greater than or equal to the outdoor temperature preset value taken for a frost layer to accumulate on the condenser and a second default parameter TN n indicative of the running time of the heat pump when an outdoor temperature is less than the outdoor temperature preset value taken for a frost layer to accumulate on the condenser in a preset defrosting interval indicatrix X when a heat pump system runs, wherein the preset defrosting interval indicatrix X=T 1 /TM n +T 2 /TN n, T 1 represents a running time of the heat pump system when an outdoor temperature is greater than or equal to the outdoor temperature preset value, T 2 represents a running time of the heat pump system when the outdoor temperature is less than the outdoor temperature preset value, and n represents the number of executed defrosting cycles; executing the defrosting cycle when the preset defrosting interval indicatrix X is greater than or equal to a preset constant value, and terminating the defrosting cycle after a defrosting cycle exit condition is met; obtaining an actual time spent on the defrosting cycle; comparing the actual time spent on the defrosting cycle with an expected defrosting time, and adjusting the first default parameter and the second default parameter when the actual defrosting time deviates from the expected defrosting time; and repeating steps S200 to S400. setting an outdoor temperature preset value, a preset constant value and an expected defrosting time; initializing a first default parameter TM n indicative of the running time of the heat pump when an outdoor temperature is greater than or equal to the outdoor temperature preset value taken for a frost layer to accumulate on the condenser and a second default parameter TN n indicative of the running time of the heat pump when an outdoor temperature is less than the outdoor temperature preset value taken for a frost layer to accumulate on the condenser in a preset defrosting interval indicatrix X when a heat pump system runs, wherein the preset defrosting interval indicatrix X=T 1 /TM n +T 2 /TN n, T 1 represents a running time of the heat pump system when an outdoor temperature is greater than or equal to the outdoor temperature preset value, T 2 represents a running time of the heat pump system when the outdoor temperature is less than the outdoor temperature preset value, and n represents the number of executed defrosting cycles; executing the defrosting cycle when the preset defrosting interval indicatrix X is greater than or equal to a preset constant value, and terminating the defrosting cycle after a defrosting cycle exit condition is met; obtaining an actual time spent on the defrosting cycle; comparing the actual time spent on the defrosting cycle with an expected defrosting time, and adjusting the first default parameter and the second default parameter when the actual defrosting time deviates from the expected defrosting time; and repeating steps S200 to S400.