Disclosed is a physical-chemical composite inhibitor for controlling spontaneous combustion of low-rank coal, and methods of preparing and using the same. The composite inhibitor consists of a chelate and attapulgite, the chelate is generated by chelation of proanthocyanidin with calcium chloride. The composite inhibitor has moisture-absorbing and moisture-retaining effect, and can reduce water dissipation at low temperature. A stable oxide insulating layer such as MgO and Al2O3 insulating layer can be formed at high temperature, which can block a coal body from contacting with oxygen. In addition, the composite inhibitor can capture hydroxyl free radicals generated during the chain-cycle reaction and destroy peroxide free radicals, and can also interact with an active moiety in coal to form a stable structure such as ether linkage and hydrogen bonding, thereby achieving permanent inhibition of low-rank coal.