The invention relates to an optical detection apparatus and a test method thereof, is applied in the field of bio-chemical analysis and especially provides an optical micro-fluidic chip sensor based on single-beam differential detection and a test method. The optical micro-fluidic chip sensor comprises a laminated structure, which includes a cover layer, a substrate, thin layers and micro-fluidic troughs. The micro-fluidic troughs are arranged on the thin layers. The micro-fluidic troughs include two or more and are arranged on different micro-fluidic troughs. In addition, the projections of the micro-fluidic troughs on the substrate are only connected to each other or are completely overlapped, so that different micro-fluidic troughs can be arranged in the same detection light wave to achieve the single-beam differential detection. The sensor and a test system thereof are simple and compact in structure and are high in test precision.