This paper presents Control of UPS inverter Using Fuzzy Gain Scheduling of PI Controller. This control scheme has Double Loop Current Mode Control Scheme in core. This scheme includes two control loops as inner and outer control loops. Inner control loop uses inductor current of inverter filter as feedback while outer control loop uses inverter output voltage as feedback. Fuzzy Logic Controller, FLC is used to adjust the voltage loop proportional-integral, PI controller parameters. ne voltage error, e and its derivative, de are used as input variables of the FLC. In this study, Fuzzy Gain Scheduling of PI Controller is simulated digitally using PSIM simulation package and C++ and implemented using Texas Instruments, TI's TMS320LF2407 DSP (Digital Signal Processor) under linear, rectifier type nonlinear and fluorescent loads. And the results show that Fuzzy Gain Scheduling of PI Controller can provide low Total Harmonic Distortion, THD and better regulation quality especially under rectifier type nonlinear and fluorescent loads.