Disclosed is a micro-lens imaging multi-well test plate which comprises: a transparent plate of 3-5 mm in thickness with one or more trapezoidal wells locating in the middle of the plate, each of the wells is of an underside of 2-4 mm in diameter, 0.2-0.5 mm in thickness, a trapezoidal dip angle of 60-75°, and has a micro-lens which upper half is hemispherical, lower half is a cylinder, with radius of 0.1˜1.0 mm, height of 0.2˜2.5 mm, molded on the bottom of the well. The micro-lens imaging multi-well test plate is made of homogeneous optical transparent materials. When the trapezoidal concave wells of the test plate are filled with fluid to immerse the micro-lens, under parallel light illumination, due to the refraction effect of light, the image of micro-lens is a round one with an outer edge that is a black ring. The outer radius R of the black ring is the radius of the micro-lens, the inner radius r of the black ring is a function of the refractive index n1 of the immersion liquid, the refractive index n2 of the micro-lens and the height h of the micro-lens, so the refractive index of the sample fluid can be determined by monitoring the value of the inner radius r of the black ring with known values of R, n2 and h. By using a multi-well test plate for imaging, the individual refractive indices of different sample fluids in all the wells can be determined simultaneously in one measurement.