Abstract: The present application discloses a compound depicted by formula (I), or a stereoisomer thereof, or a pharmaceutically acceptable salt thereof. The compound provided in the present application can bind effectively to STING and has a good agonistic action on STING protein, and exhibits a good inhibitory effect on multiple tumors. Thus, the compound provided in the present application serves as a STING agonist and can be used for treating various related conditions. The compound provided in the present invention shows a very promising prospect for application thereof in the preparation of a medicament for treating a disease associated with STING activity (in particular, a medicament for treating an inflammatory disease, an allergic disease, an autoimmune disease, an infectious disease, a cancer or a precancerous syndrome) and in the preparation of an immune adjuvant, providing a novel option for clinically screening and/or preparing drugs for diseases associated with STING activity.