MOEMS (Micro-Opto-Electro-Mechanical System) gyroscope is one of the research hotspot of international inertial domain. It combines advantages of optical detect principle of optical gyroscopes and MEMS (Micro-Electro-Mechanical System) fabrication technique. It is solid-state. It has little volume, light weight, good stability, and large dynamic scale. And it can be batch fabricated. These make it has large applications in inertial technology domain. A MOEMS interferometric gyroscope which uses spatial optical paths to sensitive Sagnac effect is presented. A spatial helical optical structure composed of micromirrors was designed. Light traveled in free space, which could reduce wastage. The gyroscope has no coupling problem, no back scatter, and no movable parts. The structure of the gyroscope has advantages in microminiaturization. It could be manufactured using MEMS technics. Theoretical analyses were made to parameters of the spatial optical path from the viewpoint of improving the fundamental detection limit. Theorem proving experiment was researched. Based on experiment design, output signals of the gyroscope on rotate platform were measured using Lock-in amplifier and other instruments. Theorem proving of the Sagnac effect is realized, and the bias stability of the gyroscope system is about 8 °/h.