Abstract: A biological detecting chip comprising an optical fiber, at least one gas filter, an upper cap and a substrate is disclosed. The optical fiber has at least one detecting area disposed on an outer surface. The upper cap has at least two guiding channels passed through the upper cap, at least one discharge channel with two ends connecting to an upper portion of distinct guiding channels, an inlet and an outlet, wherein the gas filter is attached to an upside of the discharge channel to separate the discharge channel and an outside of the upper cap. The substrate has a test area and a plurality of directing channels, wherein the directing channel connects to the inlet and the guiding channel, connects to the guiding channel and the test area, and connects to the test area and the outlet.