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Two types of uneven splitting-ratio 2×2 multi-mode interference (MMI) couplers based on silicon nanowires are designed, fabricated and characterized.The splitting ratios are 85:15 and 72:28, respectively.The devices have compact sizes and low excess losses.The footprints of the rectangular MMI region are only about 3μm ×18μm and 3μm×14μm, and the minimum excess losses (Els) are 1.30 dB and 0.82 dB.The measured splitting-ratios are consistent with the designed values.Based on their performance, these 2×2 MMI couplers are suitable candidates for the coupling section of microring resonators where a large resonance bandwidth is required for high speed signal processing.The uneven splitting capability also provides a convenient way to further optimize the Q factor and the bandwidth of the resonator