The change of the effective components (liquiritin, glycyrrhizic acid, liquiritigenin, isoliquiritigenin) contents of Glycyrrhizae Radix et Rhizoma (GRR) before and after compatibilities in Sini decoction was studied in this paper. Taking single GRR decoction, GRR-Aconiti Lateralis Radix Praeparata (ALRP) decoction, GRR-Zingiberis Rhizoma (ZR) decoction and Sini decoction as test samples, the contents changing of the four effective components of GRR were measured by HPLC. The results showed that the contents of the four effective components of GRR in the single GRR decoction was higher than that in other samples, and the sequence was single GRR decoction > GRR-ZR decoction > GRR-ALRP decoction > Sini decoction. The contents of liquiritin were 11.18, 9.89, 9.67, 9.17 mg · g(-1); the contents of glycyrrhizic acid were 20.76, 15.58, 11.30, 8.52 mg · g(-1); the contents of liquiritigenin were 0.66, 0.57, 0.45, 0.24 mg · g(-1); the contents of isoliquiritigenin were 0.14, 0.07, 0.03, 0.01 mg · g(-1). Therefore, the effective components of GRR decreased obviously after GRR compatibility with ZR providing scientific basis for GRR relieving the strong nature of ZR. The effective components of GRR decreased sharply after GRR compatibility with ALRP providing scientific support for the material foundation research of GRR reducing the toxicity of ALRP. The effective components of GRR decreased further in Sini decoction indicating that the three medicines in Sini decoction were interactional, which reflecting the scientific connotation of the mutual-restraint/mutual-detoxication, mutual-promotion/mutual-assistance compatibilities in Sini decoction.