Abstract: In model studies of soil engineering the results of monitoring the tracks of soil particle displacement may provide many Informations on soil constitutive relationship (e.g., dilatancy and compression, development of shear bands, tracks of slipping plane) and density change distribution, etc. A now approach of tracing soil particle displacement, so called direct measuring method with coordinate microscope, was suggested which has many advantages,such as great ease of realization and generalization as well as high precision. The construction of apparatus was dlscribed. This method is suitable for tests of both axial symmetry model and plane strain model. Concept and method to transform displacement field into density field and strain field were presented.Applicability of the method in two model tests of geotechnical problems was discussed. It is shown by the test results that this method is superior and promising in wide application and development.