The percolation model is used to predict the liquid distribution in a trickle bed with different packed structures. The experimental work is also performed to verify the calculated results. The effects of addition of bulking agents and the packed structure on the liquid flow rate distribution are examined. The addition of bulking agents reduces the channeling liquid flow in the trickle bed, especially when small hydrophilic particles are packed. The calculated results on the liquid distribution well reproduce the experimental data. The percolation model is proved to be a useful tool for the estimation of the liquid flow distribution in the trickle bed packed with bulking agents as in the case of the biofilter.