The present invention belongs to the field of medicinal technique, specifically relates to nitrogen-containing heterocyclic ring-substituted dihydroartemisinin derivatives and their optical isomers according to formula I or II; wherein substituent X, Y, R, R1, R2, R3 and R4 are as defined in the Description. The derivatives and compositions thereof can be prepared into clinically acceptable tablets, capsules, injections, ointments, etc., and thus have pharmaceutical uses in the treatment and/or prevention of cancers.