An electromagnetic excitation detection-based resonant tuning fork liquid density sensor comprises a tuning fork, a fixed support body, a protection tube, two magnetic cylinders, two coils, two fixing members, and a temperature sensor. The protection tube is welded on the fixed support body. The magnetic cylinders and the coils are mounted on the fixed support body via the fixing members, for cooperative use, to constitute an exciter and a detector respectively. The exciter transfers the generated alternating force to the tuning fork via the fixed support body, so that the tuning fork generates simple harmonic vibration according to the natural frequency of the tuning fork, and the vibration signal is acquired by the detector to realize detection of the tuning fork vibration frequency. The vibration frequency of the tuning fork and liquid density are in monotonic function relationship, thus real-time online measurement of the liquid density can be realized. The temperature sensor is attached to the fixed support body to real-time detect the temperature of the measured liquid, so as to compensate change in the modulus of elasticity of the tuning fork. The sensor of the invention can realize high-precision online measurement of various liquid densities at different temperatures.