Abstract: For the stress calculation of a reinforced concrete chimney under serviceability limit state, thermal stress must be considered.Based on the Code for Design of Chimneys(GB 500512002)[1] chereafter referred to as standard), it was found by the numerical analysis and theoretic study on vertical reinforcement tensile stress on windward side during service that under co-action of temperature and load(weight and wind load), there was a discontinuity in the tensile stress calculation formula in the code, therefore, the causes for the discontinuity were analyzed, and a modified calculation method of temperature stress was also proposed.