A light source control apparatus and a method for controlling light source are provided. The light source control apparatus is used to controlling N light-emitting devices connected in series. N+1 nodes are sequentially defined at two terminals of each light-emitting device mentioned above, where N is a natural number. The light source control apparatus includes a testing circuit and a compensation circuit. The testing circuit is coupled to the nodes to transmit a testing current to light-emitting devices between Ith node and Jth node, where I and J are natural numbers, and N+1>=J>I>=1. The compensation circuit is coupled to the nodes to measure a brightness of light-emitting devices between Ith node and Jth node, decide a value of a compensation current according to an intensity of the brightness, and provide the compensation current to light-emitting devices between Ith node and Jth node.