A　novel　electrochemical　sensor　for　the　detection　of　formaldehyde　is　prepared　based　on　electrodepositing　palladium　nanoparticles　on　the　Nafion　film　coated　glassy　carbon　electrode　(Pd/Nf/GCE)　through　cyclic　voltammetry　(CV).　Electrocatalytical　behaviors　of　the　modified　electrode　are　investigated　by　cyclic　voltammetry　and　differential　pulse　voltammetry　(DPV).　Experimental　conditions　are　optimized　and　a　voltammetric　method　for　determining　formaldehyde　is　developed.　Experimental　results　show　that　the　electrode　displays　a　remarked　electrocatalytic　activity　in　alkaline　solution　and　exhibits　a　linear　response　to　formaldehyde　in　the　range　of　5.0　μmol/L~5.0　mmol/L.　The　linear　regression　equation　is　ip=7.69+2.22×104c　with　a　correlation　coefficient　of　0.9967　and　the　detection　limit　is　estimated　to　be　1.0　μmol/L　calculated　from　the　signal-to-noise　ratio　of　3:1.　The　presented　methods　of　determining　formaldehyde　exhibit　good　reproducibility　and　recovery.