Measuring the refractive index of solution has important theoretical and practical implications． It studies the refractive index measurement device and method of transparent solution based on Michelson interferometer and smart phone，and applies it to quantitative measurement of the refractive index of salt and sucrose solution．The experimental results show that at the optimum working angle，the measuring device and method can quantitatively measure the refractive index of transparent liquid，the performance of the measuring device is stable，and the measuring method has high precision，about 3% and 2% respectively． Using smartphone optical sensor and free application-Phyphox to read the changes of laser interference fringes instead of human eyes，not only solves the pain point of human eye reading in traditional Michelson interference experiments，but also improves the objectivity and accuracy of the experiment．Experimental research will help to expand the application field of Michelson interferometer and smartphone in physics teaching and research， and deepen students’understanding and knowledge of wave optics and two-beam interference．