The bending deflection and hygroscopic thickness expansion of solid wood and laminated veneer lumber （ LVL） beams under load were monitored in various humidity conditions to approach the basic law of the creep in varying humidity and its relationship with the changing dimension and the difference from the creep in uniform humidity. Results showed that the total bending creep deflections （ TBCD） after 2 cycles in RH 42% →80% →42% followed by an adsorption up to 80% were 1. 80 and 1. 46 times as those in the same period in the uniform RH 80% for solid and LVL samples,respectively. The accumulated thickness expansions after the 2 humidity cycles were 0. 63% of the TBCD for the solid wood beams and 1. 27% for the LVL beams. The thickness expansion could not alter the basic law of mechano-sorptive creep of wood beams,but affected the bending creep deflection from either adsorption or desorption,especially the TBCD of the LVL.