Effects of liquid viscosity on the solid holdup and heat transfer coefficient have been investigated in the riser of a liquid-solid circulating fluidized beds, whose diameter is 0.102 m and 3.5 m in height. Glass beads (dp=1.0, 1.7, 2.1 or 3.0 mm) whose density is 2,500 kg/m(3) and aqueous solutions of carboxymethy cellulose (CMC)(μL=0.96-38 mPas) have been used as the solid and liquid phase, respectively. It has been found that the solid holdup decreases with increasing liquid velocity or viscosity, but it increases with increasing solid particle size or solid circulation rate. The heat transfer coefficient decreases with increasing liquid viscosity but it increases with increasing particle size or solid circulation rate, however, it does not change considerablely with increasing liquid velocity. The solid holdup and heat transfer coefficient have been well correlated in terms of operating variables or dimensionless groups as fellow: εS = 0.783UL(-0.100)GS(0.164)dp(0.302)μL(-0.036) h = 4349.3UL(0.010)GS(0.099)dp(0.151)μL(-0.015) (hdp/kL) = 1259(cpμL/kL)(-0.018)(GS/ULρS)(0.078)(dp/D)(1.229)