Computer simulation cardiac function values were calculated at different heart rate level, including left ventricular ejection fractions (LVEF), stroke volume (SV), cardiac output (CO) and so on, which was aimed to observe the effects of heart rate on cardiac function. It showed that the simulation results of LVEF, SV and CO were reliable at a low heart rate with linear regression model, but unreliable at a high heart rate. CO reached its maximum value when heart rate was 100 times per minute. Heart function values varied with heart rate. The effect of heart rate should be paid much attention to when heart function report was read.