Based on human ventricular single cell mathematical model, a two-dimensional mesh of ventricular wall tissue was constructed. Through the increasing of the concentration of extracellular K+, we simulated the propagation of spiral wave in a condition under the influence of ischemia in 2-D human ventricular tissue. The results showed that along with the increase of ischemic level and size, the instability of spiral waves increased, and under the influence of certain ischemic level and size, spiral waves broke up. Through this simulation study of the effects of ischemia on spiral waves in 2-D human ventricular tissue, we explained the corresponding mechanism of the maintenance of ventricular tachycardia and the cause of ventricular fibrillation under the influence of ischemia.