A computer host includes a casing, a number of fans, at least two temperature sensors, and a controller. The casing includes a top portion and a bottom portion. The bottom portion includes a first sidewall, a second sidewall, a third sidewall, and a forth sidewall. The at least two temperature sensors are positioned on the first sidewall and one or more of the other sidewalls and the top portion to sense the local temperature. The controller stores a threshold value, and when the temperature difference between the first sidewall on the one hand and the temperature of any one of the other sidewalls or the top portion is less than the threshold value, the controller turns off at least one fan.