In this paper, the influence of cooling rate on the undercooling of droplet solidification of metal melt has been investigated by employing the differential scanning calorimetry (DSC) method. The effect of cooling rate on the undercooling as well as its change tendency is analyzed theoretically. It is shown that the undercooling degree increases whereas the change rate of undercooling decreases with increasing cooling rate. Moreover, the change tendency approaches zero when the cooling rate exceedingly increased, indicating that an extremum of undercooling exists with increasing cooling rate.