The invention provides an impedance matching method, an impedance matching system and a semiconductor processing device. The impedance matching method comprises the following steps: detecting whethera radio frequency pulse is in an on or off state; if the radio frequency pulse is in an on state, calculating the value of a variable element in a matching network, and adjusting the value to a targetvalue to make the load impedance match the impedance of a radio frequency source; if the radio frequency pulse is in an off state, determining whether the load impedance is within a first preset range or whether the plasma density in a chamber is lower than a second preset value; if the load impedance is within the first preset range or the plasma density in the chamber is lower than the second preset value, keeping the value of the variable element at the target value; and if the load impedance is not within the first preset range or the plasma density in the chamber is not lower than the second preset value, adjusting the value of the variable element to an initial preset value. By using the impedance matching method, the speed of impedance matching can be increased under the premise ofensuring the success of impedance matching, and the mismatch risk of the matching network can be reduced. Moreover, when the plasma is extinguished in the pulse turn-off stage, the failure in build-up of luminance when the pulse is turned on again and the impedance mismatch caused by the low output voltage of the matching network can be avoided.