To solve the problem of state estimation of the singularly perturbed information physical systems under unknown cycle denial-of-service (DoS) attack, a design method of the event-triggered multi-time scale switching filter is proposed. Firstly, an event triggering mechanism is introduced between the sensor and the filter to determine whether the sampled data is transmitted to the network, which can save the network resources. Then, on the basis of this event triggering mechanism, considering the DoS attack problem of unknown cycle, a filtering error switching system is established. By constructing a Lyapunov function which depends on singular perturbation parameters, a switching filter design method for the singular perturbation information physical system is proposed, which reduces the estimation error, overcomes the ``ill-conditioned numerical problems" in the design process, reduces the adverse effect of DoS attack on the system in network communication, and ensures the exponential stability of the error system and satisfies $H_\infty$ performance, thus the system state estimation under unknown cycle DoS attack is realized. Finally, a circuit simulation example is used to illustrate the effectiveness of the proposed filter design method.