This article refers to the test for refractive index of high-index material (1.80＜nd＜2.00)by using a V-prism test method, and the index liquid which nd is equal to the sample need to be dropped into the linking face between V-prism and sample, in order to eliminate the sample angle of 90° processing deviation . Since the highest refractive index is only at 1.78 of existing index liquid, great nd deviation between the tested data and true value comes out in this test, and the greatest refractive index deviation has reached to 20×10-5. Now we have found out the discrepancy principle of high-index sample test data by the light refractive route research of V-prism test method. By means of calculating refractive index deviation to compensate test data, make the deviation of compensated refractive index reduce to ±4×10-5. Therefore, the measuring accuracy (±5×10-5) of high-index glass is ensured by our V-prism method.