The invention relates to a 
coal underground gasification process 
system. The 
coal underground gasification process 
system comprises a gasification agent injection 
drill hole, 
coal gas outlet 
drill holes, a main gasification channel, 
branch gasification channels, a 
drill hole supporting tube, a gasification agent injection tube, a 
combustion agent injection tube, a sealing device and an 
ignition point shifter. The gasification agent injection 
drill hole is connected with the 
coal gas outlet drill holes through the main gasification channel and the 
branch gasification channels, and the 
combustion agent injection tube is sleeved with the gasification agent injection tube and is connected through the sealing device. A gasification process includes the steps of carrying out ignition, judging whether 
water vapor is fed into, feeding into 
water vapor, judging whether an 
ignition point is moved forward, starting the 
ignition point shifter and continuing to conduct 
combustion. The coal underground gasification process 
system has the advantages that the transverse gasification area and longitudinal gasification area can be enlarged, coal reserves for gasification are increased, autoignition and controllable back gas injection are achieved in a well-free coal underground gasification process, meanwhile the problem of 
short circuit of gasification agents in the gasification channels is solved, the probability of back mixing of 
product gas and the gasification agents is lowered, and safety operation of the gasification process is guaranteed.