The invention discloses a method for the computer aided design of a microwave filter. The method comprises the following steps of: 1) determining the size of a resonator according to the center frequency of the filter; 2) determining a group of standard delay amounts Gamma1, Gamma2, ..., GammaN according to the bandwidth and order N of the filter; 3) simulating a single-port network consisting ofan input port and a first-order resonator, and regulating the physical size of the first-order resonator to make the port delay characteristic of the network meets Gamma1; 4) adding a second-order resonator, and regulating the physical sizes of the first-order and second-order resonators to make the port delay of the network meets Gamma2; 5) by parity of reasoning, obtaining the physical sizes ofa half of resonators; and 6) mirroring the resonators with the regulated physical sizes to obtain the sizes of the other half of resonators to finish the design of the filter. In the method, the delay characteristic of the single-port filter is utilized, and the method has the advantages of small calculated amount and high efficiency as well as high center frequency and bandwidth setting accuracy, and is particularly suitable for the computer aided design (CAD) of the high-order microwave filter.