This article presents a nano-g microopto-electromechanical system (MOEMS) accelerometer that uses the principle of Fabry-Perot (F-P) interference in conjunction with a micromechanical structure for transducing input acceleration. The device comprises a movable silicon proof mass suspended by silicon flexural beams and an F-P cavity integrated with a cleaved optical fiber. Furthermore, a closed-loop force balance mechanism is exploited to enhance the accelerometer's measurement range by utilizing magnetic force provided by a pair of permanent magnets. Comprehensive characterizations are conducted to evaluate the performance of the proposed device. The scale factor of the MOEMS accelerometer in a closed-loop configuration is determined as 9.2 V/g with a working range of +/- 1 g. Benefiting from the electromagnetic force balance, the dynamic range (DR) of the device is up to 157 dB@30 Hz, with the lowest noise floor of 10 ng/root Hz and a working bandwidth of 500 Hz. The results validate the functionality of the MOEMS accelerometer, particularly highlighting its favorable DR and working bandwidth, thus enabling a broad range of applications, such as seismic, gravity exploration, and navigation.