The invention discloses a sulfite detection reagent and a detection method thereof. The reagent comprises the following ingredients: 5,5-dithio-bis(2-nitrobenzoic acid), sodium tetrachloromercurate, pararosaniline hydrochloride, acetic acid, barium chloride, foamed aluminium, sodium bicarbonate, chitin, sodium molybdate, formaldehyde, glycerin, zinc acetate and water. The detection method comprises the following process: crushing a sample when the sample to be tested is a solid and then adding deionized water, decocting with slow fire, filtering and taking a filtrate, adding 1-3 droplets of the sulfite detection reagent into the filtrate, standing for 1-3 min, and observing color change (the solution turns amaranth when concentration value of sulfite is higher than 0.08 microgram / g; and the solution will not change color when concentration value of nitrite is lower than 0.08 microgram / g); and directly dropwise adding the sulfite detection reagent if the sample to be tested is a liquid.The test paper can rapidly detect content of sulfite in food, is convenient to transport and carry, and is convenient to operate.