To prove the sixport networks can be used for the readout circuit of BAW sensor, the equivalent circuit model of the BAW sensor consisting of FBAR and microstrip sixport network is established. The Mason equivalent circuit model of FBAR is established, and the equivalent circuit model of the microstrip sixport network is established in ADS software.The port 1 of the microstrip sixport network is connected with the radio frequency source, the port 2 is connected with the FBAR, the other four ports are respectively connected with four 50 ohm resistors which are used to read the power per port. The FABR reflection coefficients are solved by the radical center method and the average method respectively and two reflection coefficients v.s frequency curves of FBAR are obtained. The advantages and disadvantages of two kinds of approximate calculation method of the reflection coefficient are analyzed, and the method of increasing the operating bandwidth of the sixport network is also analyzed. The results of simulation show that the microstrip sixport network can accurately measure the reflection coefficient v.s frequency curves of the FBAR, hence the six port network can be used for the BAW sensor readout circuit.