A　method　for　measuring　the　channel　size　of　microfluidic　chip　by　using　optical　coherence　tomography　(OCT)　is　investigated.　Based　on　spectral-domain　OCT　imaging　and　image　processing,　an　OCT　system　for　measurement　of　the　microfluidic　channel　size　is　developed,　which　is　suitable　for　planar　two-dimensional　measurement.　The　cross-sectional　images　of　the　micro-channel　of　a　microfluidic　chip　are　obtained　by　using　OCT　continuous　B-scan　technology.　With　image　processing　for　the　acquired　image　in　noise　elimination　and　dispersion　compensation,　the　size　of　the　micro-channels　in　depth　is　achieved.　Comparing　with　the　single-scan　OCT　imaging　mode,　back-passing　multiple-scans　mode　has　the　capability　of　high　image　quality　to　achieve　high　measurement　precision　of　micro-channel　size.