It was found that there was a periodic mechano sorptive creep（MSC） behavior of the wood I beam（IB） in an indoor natural moisture changing environment. Results from the experiment and analysis to approach the static bending creep of the IB in January to March in Kunming indicated that the deformation decreased in the wetting period but increased in the drying period. However, its daily MSC behavior was quite different from the basic law of the MSC. Furthermore, the whole creep behavior of the IB in the indoor natural moisture changing environment was similar to a normal creep of solid wood. The total deflection of the IB, which was flanged with PF LVL of poplar and webbed with bamboo OSB, in 90d was 533mm, in which, the deflection in the first stage creep and the irreversible deflection unloaded after 14d were 138,179mm, which occupied 259%,336% of the total deflection respectively.