In the biodegradation of Formaldehyde gas with a biotrickling filter, a portion of Formaldehyde is solved in the recirculating trickling liquid. As a consequence, the treatment efficiency is limited. The study explored the feasibility of removing the liquid-phase formaldehyde by inducing chemical reactions in the trickling liquid. Experiments were conducted to test three chemicals (sodium sulfite Na2SO3, sodium bisulfite NaHSO3, and ammonium chloride NH4Cl), which were applied in the trickling liquid, respectively, to react with the formaldehyde. The formaldehyde removal efficiencies were compared and the optimal reaction Molar ratios were investigated. The results showed that Na2SO3 brought the highest Formaldehyde removal efficiencies among the three chemicals and the optimal reaction Molar ratio of Na2SO3 and Formaldehyde was 3:1. Under the condition, the removal efficiency of the liquid-phase Formaldehyde was high up to 99.91%.