The particle entrainment rate was measured and discussed in a cold model fluidized bed(0.1m-ID, 2.4m-height) which employed a secondary air injection at a height of 0.2m above the distributor plate. Sand particles of mixed sizes under 0.5mm in screen size were used as bed materials. The particle size(0.128-0.363mm), the overall superficial gas velocity(0.76-2.77m/s), the secondary air fraction(0-0.5), and the static bed height(0.1-0.3m) were considered as experimental variables. The entrainment rate increased with the gas velocity, but with a decrease of particle size. The effect of static bed height was negligible. The entrainment rate decreased with an increase of the proportion of secondary air. The effect of secondary air fraction was appreciable for over-bed injection and was reduced as the location of second gas inlet moved toward in-bed.