A biomolecular sensor system utilizing a transverse propagation wave of surface plasmon resonance (SPR) is described. The system comprises: a substrate; a dielectric layer, having a groove therein and standing on top of the substrate; a sensing film layer, sitting at the groove; a pair of prism devices, each resting on one side of the groove and both separating a tunable distance. Besides, the sensor system further comprises a light source, a light detector (a frontend of which connecting to a spectrometer and a backend connecting to a differential amplifier) and a channel with a cover forming inside the groove for the acquisition of the reflected light from the prism devices. Since the sensor system is constructed by exploiting the SPR technique on the transverse propagation, a whole contact surface is under detection (parallel detection) which differentiates it from the traditional method of single-area SPR detection. The sensor system is applicable not only for the far-infrared remote sensing with a transverse distance of several centimeters, but further for the biomedical sensing applications in the miniature sizing and high throughput.