The M5′ model tree algorithm is used to on-line identify and draw the accurate and detailed single and double extraction unit working condition charts. This method automatically and optimally selects the number of sections and approaches the nonlinear consumption curves might be with non-convex and discontinuous property using piecewise linearization fitting. By comparison of scrolling identified characteristics at a fixed period， the change of unit can be detected and an awareness visualization tool of unit can be achieved. This method can provide the check basis for measured data and provide accurate piecewise linearization function of unit characteristics for load optimal sharing of thermal power plant and energy saving scheduling of the power grid.