Abstract: Platinum particles were electrochemically deposited on glassy carbon electrodes modified by carbon nanotubes. The chemically modified glassy carbon electrodes with platinum particles and carbon nanotubes (Pt/CNTs/GCE) were used as formaldehyde sensors. Electrochemical behaviors of formaldehyde at Pt/ CNTs/GCE were investigated by cyclic voltammetry (CV) and linear scan voltammetry (LSV). Experimental conditions were optimized, and a voltammetric method for determining formaldehyde was developed. The experimental results show that the optimum accumulation potential is - 0.1 V and the optimum accumulation time is 180 s. A highly linear response to formaldehyde in the concentration range of 8.0umol/L- 1.0 mmol/L was observed in 0.01 mol/LH₂SO₄, with a detection limit of 3.0 umol/L estimated at a signal-to-noise ratio of 3: 1. The presented method of determining formaldehyde exhibits high sensitivity and good reproducibility.