Provided is a 8,9-dihydroimidazole[1,2-a]pyrimido[5,4-e]pyrimidine-5(6H)-ketone compound. In particular, provided is a compound of formula (I), or a pharmaceutically acceptable salt or prodrug thereof, wherein A and R1-R7 are as defined herein. The compound of formula (I) is a Wee1 kinase inhibitor. Therefore, the compound of the present invention can be used to treat diseases caused by abnormal activity of Wee1.