A light sensing method applied to a light sensing system comprising a first light sensor and at least one light source. The first light sensor comprises a plurality of light sensing units. The light sensing method comprises: (a) respectively controlling an exposure condition for each of the light sensing units according distances between each one of the light sensing units and the light source; and (b) controlling the light sensing units to sense the light from the light source according to the exposure condition. The light sensing system can have a better SNR via adjusting the exposure condition for each one of the light sensing units. Such light sensing method can be applied to compute physiological parameters.