The creep test of two types of wood rectangular beams and three types of wood I-beams under indoor natural environment in Kunming were conducted for 200 d using a self-developed full-size wood beam creep test system. The relationship between moisture content and relative humidity was analyzed. The results show that the changes in moisture content of the wood beams significantly lag behind the changes in relative humidity and the lag in the absorption is greater than that in the desorption. The average creep rates of two types of wood rectangular beams and three types of wood I-beams in four typical relative humidity change periods of low humidity fluctuation， high humidity fluctuation， rising humidity continuous fluctuation and declining humidity continuous fluctuation are 8.839×10^-2，1.183×10^-2，-1.730×10^-2/-3.598×10^-2 and 7.424×10^-2/9.007×10^-2 mm/d respectively. The mechanical absorption creep characteristics are obvious. The FB₉₀ （ratio of creep deflection at 90 d to creep deflection at 1 min） of seven beams is less than 1.60， which meets the creep resistance requirement of beams for load-bearing. The creep resistance of wood rectangular beams is better than that of wood I-beams.