Precipitation reaction of glycyrrhizin (I) with 32 kinds of alkaloids including synthetic bases and 10 kinds of crude drugs which contain various types of alkaloids in aqueous solution was investigated and following results were obtained. 1) Tertiary alkaloids which had heterocyclic aromatic rings or nitrogen atoms neighbouring to aromatic ring or conjugated olefine systems in the structure, namely, papaverine, noscapine, emetine, O-methyl domesticine, domesticine, nornuciferine, dl-tetrahydroberberine, l-corydaline, quinine, reserpine and sinoactine gave precipitate, while other types of alkaloids, namely, l-ephedrine, N-methylephedrine, l-phenylalaninol, atropine, l-scopolamine, cocaine, morphine, ethylmorphine, codeine, hydrocodeine, thebaine, sinomenine, aconitine, physostigmine, caffeine, pethidine did not. 2) Tertiary alkaloids which had pK_a values smaller than 7.5 were likely to precipitate with I, while those which had pK_a values larger than 7.5 did not. 3) Among quaternary alkaloids, berberine and coptisine produced precipitate, while menisperine, N-methyl scopolamine and neostigmine did not. 4) Among crude drugs which contained various alkaloids, coptis rhizome, corydalis roots, phellodendron cortex and evodia fruits gave precipitate with I in aqueous solution, while aconite roots, areca seeds, ephedra herb, magnolia cortex, nupharis rhizome and sinomenium roots did not.