Abstract: Based on the elastic theory of a thin plate and the idea of age-adjusted modulus method, the creep effect on rectangular thin reinforced concrete plates is analyzed. The differential equation of elastic curve is established considering the effect of concrete creep and steel restraint, and the formulae for calculating creep effect on rectangular thin reinforced concrete plates with four simply supported sides and four fixed sides are respectively deduced, which can calculate the deflection of the plate and stresses of concrete and steel at anytime.