Guanidine isothiocyanate is a white crystal with a melting point of 116~121 ℃. At 20 ℃, the pH value of 6mol/L in water is 4.5~6, and the solubility is completely dissolved. It is an uncoupler and a kind of strong protein denaturant, which can dissolve protein and make the secondary structure of protein disappear, cell structure degrade, and nucleoprotein quickly separates from nucleic acid. Used for denaturing and splitting cells; Rna and dna were extracted without rnase and dnase activity.