The invention discloses a secondary frequency signal detection technology-based resonant fiber optic gyroscope light source intensity modulation noise inhibition method and device. The device comprises a tunable semiconductor laser, an isolator, a 50% coupler, a first path phase modulator, a second path phase modulator, a first path signal source, a second path signal source, an input end 95% coupler, an optical fiber ring resonator, an output end 95% coupler, a first path photoelectric detector, a first path lock-in amplifier, a frequency servo loop, a third path lock-in amplifier, a third path signal source, a second path photoelectric detector, a second path lock-in amplifier and an intensity compensation algorithm module. The method and device effectively compensate a gyro output error caused by laser optical power change, improve a gyro output precision, utilize an intensity compensation algorithm realized only through codes, realize real-time compensation and are free of other optical devices and electrical modules. The device has a simple structure and is conducive to system miniaturization.