The protective effects of Da Chai Hu Granules (DCHKL) on islet cells which were incubated with 4 mmol x L(-1) alloxan (AXN) were studied. The viability of islet cells were measured with MTT. Insulin released into medium and in islets was detected by radioimmunoassay. Cell apoptosis rate was determined by flow cytometry. The expression of anti-apoptotic gene Bcl-2 and pro-apoptotic gene Bax in islet cells were measured with RT-PCR (reverse transcription polymerase chain reaction). Serum containing DCHKL can promote the activity of islet cells significantly (P < 0.01). Basal insulin secretion and high glucose-stimulated insulin secretion increased significantly (P < 0.01). Serum containing DCHKL can inhibit apoptosis of islet cells, the ratio of apoptosis was decreased. Serum containing DCHKL increased expression of Bcl-2 mRNA and decreased expression of Bax mRNA. DCHKL can significantly promote proliferation of islet cells and increase the amount of basal secretion of pancreatic islet cells and high glucose-stimulated insulin secretion. The expression of Bcl-2 increased significantly. The expression of Bax decreased significantly. DCHKL have a protective effect on the islet cells.