The Slot structure is superior in improving the sensitivity of integrated optical waveguide sensor and decreasing the detection limit. The microring optical biosensor based on PSQ-Ls polymer waveguide with the slot structure is studied. The influence of height, width and slot width of the Slot waveguide on the sensitivity is analyzed at the 850 nm band, and the optimized cross section parameters of microring sensor are gained for the single mode transmission. The bend loss and free spectral range of the Slot waveguide microring are analyzed, and the relationship between structural parameters and performance of microring sensor, such as extinction ratio, quality factor, is obtained. The optimized bend radius and coupling efficiency of the microring are achieved. Compared to the ridge waveguide based microring sensor, the Slot waveguide based microring sensor has twice of the sensitivity and a half of the detection limit.