The purpose of this study is to explore the recurrence risk of cardiovascular events in patients with type 2 diabetes mellitus and coronary heart disease after different antidiabetic drug therapy (glipizide or metformin) by using an double-blind, randomized, parallel control and prospective study

The end point of this study is:

1. follow up 3yr
2. recurrence of cardiovascular event
3. death caused by other reasons such as stroke, uremia, blindness and amputation

Inclusion Criteria:

• Coronary heart disease
• Type 2 diabetes

Exclusion Criteria:

• Severe organ dysfunction, psychopathy, infection, neutropenia
• Congenital heart disease, rheumatic heart disease, severe arrhythmia, myocardiopathy