The invention discloses a dimming control circuit of an LED lamp. An input voltage regulation module is used for adjusting an input voltage range and outputting a periodic circular half-sine wave voltage, a first LED lamp string current branch regulation module and a second LED lamp string current branch regulation module which are connected with the input voltage regulation module can be used for forming different series-parallel current branches with the change of the input voltage, the first LED lamp string current branch regulation module and the second LED lamp string current branch regulation module are connected in parallel with a capacitor C1, and voltage dimming and low frequency flash can be achieved. The dimming control circuit of the LED lamp is suitably used for wide-range voltage input, is high in power factor, simple in structure and low in cost, and is convenient to operate and easy to implement.