The invention relates to a method for simulating and modeling a controlled object in a distributed control system (DCS) of a thermal power generating unit. The method for simulating and modeling a main analog controlled object comprises the steps of: a, calculating water feed pressure, feed water flow and separator pressure parameters in a simplification manner according to the rotation speed of a water feed pump; b, simplifying a water level of a steam drum/separator into the integral of a flow difference between an inlet working medium and an outlet working medium; c, determining steam flow by calculating the dryness of the working media; d, calculating temperature based on the pressure and enthalpy by using an integrating function of a PID (Proportion Integration Differentiation) module, and then simulating to calculate main steam temperature; e, simulating to calculate smoke quantity and the suction capacity of a draught fan, and further simplifying and simulating the negative pressure of a discharge hearth; f, simulating to calculate the combustion capacity of a boiler according to the rotation speed of a coal feeder; and g, simulating to calculate a unit load according to the combustion capacity or the main steam flow. According to the invention, by means of a simulation method for establishing a controlled object simplified model inside a DCS system by adopting a DCS configuration tool, the control over a closed loop is realized.