This paper mainly studies the deflection under short-term loading of recycled course aggregate reinforced concrete beam is calculated by using of the formula of short-dated rigidity in code for design of concrete structures. According to testing the flexural performance of 6 recycled course aggregate beams with the same section size, different replacement ratio of recycled coarse aggregate of 0%, 50%, 70%, 100% respectively and different percentage reinforcement of 0.68%, 0.89%, 1.13% respectively, analyzes relation between deflection and replacement ratio of recycled coarse aggregate, deflection and percentage reinforcement, compare measured value and calculated value using of current codes and make statistical analysis this data . By regressing and analyzing the experimental data from literature, supplied short-dated rigidity modified formula of recycled course aggregate beam. The calculation results are in good agreement with the experimental data. The formula of short-dated rigidity can accurately calculate deflection under short-term loading of recycled course aggregate reinforced concrete beam, and can be referenced in engineering practice and correlative regulations.