Objective　In problem-based learning， students are often found difficult to con-struct medical knowledge systematically and transfer knowledge to solve new problems. In face of this challenge， this study aims to investigate the effect of visualization tool-supported online problem-based learning on medical students' clinical diagnostic expertise development. Methods　A controlled study was conducted and 52 medical students were randomly assigned into experimental group （using visual-ization tool-supported online PBL environment for learning） and control group （using online PBL envi-ronment for learning without visualization tool support）. Participants were asked to complete the diag-nostic analysis of three kidney problems according to the requirements of the learning environments and to provide feedback of online learning experience afterwards. Paired-sample t test and one-way analysis of vonriance were used to analyze both group's case 1 and case 3 on line learing scores. Results　The results revealed that the experimental group had significant improvement in online learning performance [case 1： （1.47±0.54）， case 3： （2.14±0.55）， P=0.015]， while the control group had no significant improvement [case 1： （1.57±0.67）， case 3： （1.66±0.49）， P=0.234]. Early performance of online learning and group factor had interative effects （F=7.266， P =0.013）. Conclusions　The findings suggest that visualization tool-supported online PBL environment can facilitate medical student clinical diagnostic expertise development effectively.