Method for investigating formol

The invention discloses formaldehyde detecting method. It includes the following steps: preparing formaldehyde detecting agent as 0.1-0.4g fuchsine/100ml water to dissolve at 40-80 degree centigrade; orderly adding sulfurous acid or sodium sulfite and concentrated sulphuric acid wit density 80% to make detecting agent with 100/16-20/3-5 volume ratio; putting cotton into the detecting agent to form medicine bearing cotton; putting it into sealing sleeve between piston and pinhead; using pinhead to adsorb detected liquid to make it contact with the cotton; if its color changes, the formaldehyde content is not less than 1ppm. The method of the invention has safe using, high correct rate, especially suits for on-site measurement.