Fixed-time synchronization of complex networks is investigated in this talk. Firstly, three completely novel lemma is introduced to prove the fixed-time stability of the equilibrium of a general ordinary differential system, which is less conservative and has a simpler form than those in existing literature. Two kinds of controllers have simple form, and the other one apply intermittent control with periodically and non-periodically. Then sufficient conditions are presented to realize synchronization of complex networks (with a target system) within a settling time via three different kinds of simple controllers according to the novel lemma. In general, controllers designed to achieve fixed-time stability consist of three terms and are discontinuous. However, in our mechanisms, the controllers only contain two terms or even one term, and are continuous. Besides, the controller only work in their control time, which save the cost and has more practical applicability.