To monitor coal supply and ensure secure operation of the power system， the coal supply security early warning system is studied. First a coal supply model based on system dynamics theory is developed and the related influencing factors affecting coal supply are analyzed in detail. Meanwhile， the index system characterizing coal supply based mainly on inventory is set up. On the basis of warning degree classification， the coal supply security early warning system based on fuzzy comprehensive evaluation and analysis is proposed. Finally， the system is tested by monitoring the 100 MW and above coal fired power plants of an example province. The state of coal supply is effectively represented by the warning degree， according to which the electricity market supervisory agencies are able to take timely countermeasures.