Provided in the present invention are a compound represented by general formula I, a pharmaceutically acceptable salt, enantiomer, diastereoisomer or racemate thereof, a preparation method therefor, a pharmaceutical composition containing same, and a use of same in the preparation of drugs for treating diseases or conditions mediated by EED and/or PRC2. The compound of the present invention can be used for treating PRC2-mediated diseases or conditions. (I)