This paper studies the formation control for unmanned aerial vehicles (UAVs) under communicationdelay and wake disturbances, in which the inner-loop and outer-loop control strategy is adopted. Firstly, as for thedynamical models of follower UAVs, the wake interferences are considered and their influences are respectivelyestimated by using the sliding model disturbance observers (SMDOs). Secondly, since the outer-loop informationin the UAVs exchanges via communication network, by adding an internal dynamic variable, an adaptive memorybased event-triggered mechanism (METM) is proposed to alleviate transmission burden with maintaining idealcontrol performance. Thirdly, by using the designed METM and an intermediate vector, a sliding mode controller isderived to accomplish the desired control target, which can compensate the communication delay in control input. Fourthly, as for the overall closed-loop system, a sufficient condition on asymptotical stability is established and aco-design method of checking the triggering parameters and controller gains is expressed in term of linear matrixinequalities (LMIs). Moreover, in order to tackle the wake interferences of the inner-loop, an adaptive attitudetracking controller is put forward to ensure the bounded stability of tracking errors by solving the reference signal. Finally, a simulated example is exploited to illustrate the validity of the proposed scheme.