Abstract: In this study, we investigated the running-in behavior of brass (i.e. 64% copper and 36% Zinc) sliding against 100Cr6 under lubricated conditions on a tribometer based on in-situ holographic microscopy and radionuclide technique. The corresponding relationships between coefficient of friction, surface roughness and wear rate of brass was studied. On this basis, the wear model for surface roughness was established. Moreover, the wear model was evaluated by method of fitting goodness. In the beginning of experiment, the surface of CuZn36 revealed rough being accompanied by high wear rate. For the remainder of the test, wear-resistant layer was gradually formed in the near-surface region of the wear track. Meanwhile, surface roughness and wear rate decreased and tended to be stable. The fitting goodness of wear model was 90.23%, which means that the model can predict wear rate effectively under certain working conditions.