The invention relates to a chaos particle swarm based thermal power unit load optimal distribution method, which comprises the steps of fitting a coal consumption characteristic curve according to coal consumption characteristic parameters of a power generating unit, establishing a load optimal distribution model, converting the load optimal distribution model into a non-restraint problem through a penalty function method, distributing the total generation power to each unit by being combined with a chaos particle swarm algorithm, and finally acquiring an optimal load distribution result of each unit. Compared with the prior art, the method provided by the invention can distribute the optimal output point of each power generating unit scientifically and reasonably under the given total generation power, thereby enabling power supply coal consumption of the unit after optimization to be obviously reduced.