The invention provides an anti-weld-omission system for a welding tool for stud welding. The anti-weld-omission system comprises an air cylinder and a main air source. The air cylinder comprises a piston cylinder and a rear cylinder. The main air source is connected with three air supply branches. The first air supply branch is connected with an air inlet of a double-pneumatic two-position five-way valve. The second air supply branch is connected with an air inlet of a two-position four-way valve. The third air supply branch is connected with an air inlet of an electromagnetic valve. A first air outlet of the two-position five-way valve is connected with the piston cylinder of the air cylinder. A second air outlet of the two-position five-way valve is connected with the rear cylinder of the air cylinder. A first air outlet of the two-position four-way valve is connected with a first pneumatic port of the two-position five-way valve. A second air outlet of the two-position four-way valve is connected with a first air inlet of an AND valve. An air outlet of the electromagnet valve is connected with a second air inlet of the and valve. An air outlet of the AND valve is connected with a second pneumatic port of the two-position five-way valve. The anti-weld-omission system further comprises a sensor used for detecting weld positions of stud welding of each time, and the electromagnetic valve is directly or indirectly connected with the sensor. By the adoption of the anti-weld-omission system, the weld quality is reliably guaranteed, and therefore the product quality is guaranteed, and the safety is good.