The invention discloses a method used for a gas drilling drillstem test, which relates to the technical field of petroleum and natural gas drilling methods. The method comprises the following steps of: firstly, connecting an inner blowout pipeline, a throttle manifold, a ground testing device and an outer blowout pipeline in sequence, wherein the adopted ground testing device comprises a manifold which is connected with the gas drilling outer blowout pipeline in series, and a first flat valve, a second flat valve, a third flat valve an a measurement unit; secondly, when a drillstem test is carried out, firstly opening the third flat valve, subsequently opening the second flat valve and finally closing the first flat valve, and at this moment, gas firstly flows through the inner blowout pipeline, then arrives at the throttle manifold and then enters the ground testing device for testing and finally is blown out by the outer blowout pipeline to be ignited. The drillstem test can be carried out before blowout and pollution discharge by adopting the method, and the test can be carried out at any time in the drilling process. A flowmeter adopted in the method can be very conveniently changed when being broken.