1. The intuitive method is to smell and taste. Generally, the methanol in red wine is within 4mg/L, which is a normal standard. If it exceeds this amount, it will be harmful to human body. Usually, methanol and other fusel exceed the standard, which can be tasted through many times of comparative tasting or separate tasting, but it cannot be accurately quantified. 2. The accurate quantitative method can be measured by "chromotropic acid spectrophotometry", which belongs to laboratory tests and requires instruments and reagents. The principle is very simple, that is, chemicals react with methanol to produce formaldehyde, which is then condensed with chromotropic acid and oxidized into quinone-structured blue-purple compounds. Finally, it can be quantified by comparing with the standard series. 3. If there are dizziness, nausea, head-up and other adverse reactions after self-brewing, it is generally that fusel exceeds the standard and should be stopped.