Fine NP-AgAu (nanoporous AgAu) alloys with spongy structure was fabricated by chemical dealloying from rapidly solidified amorphous precursors Ag38.75?xCu38.75Si22.5Aux (x=0, 0.5, 1 and 5). The results indicate that the addition of small content Au in precursor can refine both the ligaments and pores obviously. Among the present components of the precursors, NP-AgAu alloys dealloying from Ag37.75Cu38.75Si22.5Au1 had the finest spongy structure. The size of pores was 5-10 nm and the grain size of ligaments was 10-20 nm. It also had the highest surface area of 106.83 m2g?1 and the best catalytic activity towards electro-oxidation of formaldehyde with the peak current of 665 mA mg?1.