An LED lamp and a power supply module thereof are provided. The power supply module includes a driving circuit, a OVP circuit, and an impedance detection circuit. The OVP circuit is configured to determine whether an OVP condition is detected by sampling the driving signal, and the impedance detection circuit is configured to determine whether a user touching state is detected. When either the OVP condition or the user touching state is detected, the power switch of the driving circuit will be controlled to limit the amount of a current flowing through the power switch. In addition, the impedance detection circuit could detect the user touching state by comparing signals with a defined level sampled during each pulse, thus enhancing the detection accuracy.