摘要： Sensitivity is a critical characteristic of sensors, and increasing the sensitivity of the sensor is valuable for measurement study. Incident power has an important influence on the sensitivity of magnetic fluid sensors based on optical transmission properties. Variation in the magnetic field sensitivity at different incident powers was investigated by the measurement of transmitted power through the magnetic fluid sensors. As the magnetic field strength increases, the sensitivity variation of the magnetic fluid film sensor can be divided into four stages: first decreasing sharply, secondly increasing, then decreasing gradually, and finally tending toward a small stable value. The magnitudes of the change in the sensor sensitivity are influenced by the incident power, because the structural pattern of the nano-magnetic particles in the magnetic fluid sensor changes, the Soret effect and the Photonic Hall effect co-define the sensing system. In the weak magnetic field range, when a higher sensitivity is required, it is appropriate to select a larger incident power; however, in a large magnetic field range, when a higher sensitivity is required, a small incident power should be selected. Therefore, the magnetic fluid film sensor exhibits different sensitivity characteristics if different incident power values are chosen. The appropriate incident power can be selected according to the range of the magnetic field to be measured to improve the sensitivity in the magnetic field measurement study.