The invention discloses a Caspase-3 inhibitor, namely a dihydropyrrolones derivative, with a molecular structural formula (1), and pharmaceutically acceptable salts thereof. In the molecular structural formula, R1 represents alkyl, aryl or heterocyclic radical; R2 represents hydrogen, alkyl, aryl or heterocyclic radical; R3 represents alkoxyl, aryloxy, primary amino radical or secondary amino radical; and R4 represents primary amino radical, secondary amino radical, alkoxyl, aryloxy, alkylthio radical, arylthio radical or N-containing heterocyclic radical. The dihydropyrrolones derivative or the pharmaceutically acceptable salts thereof, as a Caspase-3 inhibitor, can be applied to treating diseases caused by excessive apoptosis of cells, such as acquired immunity deficiency syndrome, serious hepatitis, osteoarthritis, senile dementia, Parkinson's disease, amyotrophic lateral sclerosis, Huntingdon's chorea, spinal and cerebellar ataxia, muscular dystrophy, cerebral ischemia, cerebral injury and the like, singly or by combining with other medicines.