This paper presents a new topology of uninterruptible power supply (UPS) by using a Z-source inverter, where a symmetrical LC network is employed to couple the main power circuit of an inverter to a battery bank. Using passive diode rectifier is known to constrain the converter to operate in only the forward power transfer mode, and generally support only voltage buck or boost operation, which to some extent constrains its disturbance ride through ability. The Z-source converter overcomes the conceptual and theoretical barriers and limitations of the traditional voltage-source converter and current-source converter. The Z-source concept can be applied to all dc-to-ac, ac-to-dc, ac-to-ac, and dc-to-dc power conversion. With this new topology, the proposed UPS can maintain the desired ac output voltage at the significant voltage drop of the battery bank with high efficiency, low harmonics, fast response, and good steady-state performance. The entire system is simulated by MATLAB\SIMULINK and the results are verified experimentally.