Provided are a pyrazolo[3, 4-d]pyrimidin-3-one derivative as shown in formula (I) or (I' ) and/or a pharmaceutically acceptable salt thereof, and a composition containing the compound as shown in formula (I) or (I' ) and/or the pharmaceutically acceptable salt thereof, a preparation method and the use of same as a Wee1 inhibitor, and the use of same as a sensitizer during chemotherapy or radiotherapy for cancers. The compound can effectively inhibit the Wee1 and related signaling pathways and has good effects in terms of treating and/or alleviating cancers.