The invention relates to a method for predicting and controlling steam temperatures of boilers on the basis of a state observation model. The method includes 1, replacing heat exchangers by multiple sections of concentration parameter links by a principle of natural segmentation or virtual segmentation, and using outlet parameters of media of various sections as representative parameters of the concentration links to build a mathematical model of enthalpy and temperature channels of the heat exchangers; 2, creating a state observer on the basis of output feedback and estimating outlet temperatures of the various sections; 3, connecting an MPC (multivariate model prediction controller) and a PID (proportion, integration and differentiation) regulator in a cascade manner to form a serial control circuit, acquiring step response coefficients according to the model of the enthalpy and temperature channels of the heat exchangers and acquiring set values of lead temperatures; 4, regulating the steam temperatures by the inner-loop PID regulator according to difference among the lead temperatures and output of the MPC and acquiring control signals of attemperation water valves. The method has the advantages that model building and verification are carried out, so that field test requirements can be reduced; states of inertial and lagged controlled objects are reconstructed via the state observer, so that characteristics of the objects can be modified; prediction and control are implemented, so that targets can be accurately and quickly controlled.