The invention discloses a chaos optimization method for on-line coal quality parameter calculation, which includes the following steps: the real-time parameters of a thermal power unit, such as the coal feed quantity of a coal feeder, the primary wind flow and primary wind temperature of the inlet of a coal pulverizer, the wind-powder mixture temperature of the outlet of the coal pulverizer and the power of the coal pulverizer, are acquired; the parameters of intermediate unknown variables, such as carbon dioxide gas volume, sulfur dioxide gas quantity calculated according to dry basis components and carbon dioxide gas quantity calculated according to dry basis components in exhausted flue gas, are set; a chaos optimization algorithm is adopted to jointly work out the dry ash-free basis component, dry ash-free basis hydrogen component, dry ash-free basis oxygen component, dry ash-free basis nitrogen component and dry ash-free basis sulfur component of coal, as-received basis moisture, as-received basis ash and net calorific value. The method utilizes the real-time soft measurement technology of analyzing as-fired coal elements and net calorific value by using the chaos optimization algorithm to work out the real-time information of coal quality.