The invention relates to an on-line safety evaluation method for water-cooled walls. The method comprises the following steps: arranging a small amount of test points in the pipeline section with typical flow heat transfer in each radiation zone, combining with the existing test points at the entrance and exit outside the furnace, calculating and checking the characteristic parameters of the inner wall of the water-cooled wall of the station boiler, inputting to a computer for calculation, performing the on-line real-time calculation of the Parameters such as pipeline flow, entrance and exit pressures, enthalpy value, lengthwise furnace inner wall temperature of each pipeline section and stress change value, to judge whether the dangerous factors exist, such as hydrodynamic instability, over-temperature and creep fatigue, displaying the calculation results in real time, recording the data as judgment basis of safe operation of the water-cooled wall. The invention realizes the optimal operation of equipment, manages the repair and maintenance based on the operational state, and ensures the state maintenance and repair of equipment.