OBJECTIVE: To study the relation between of forming time red blood cell aggregation body and structure by changing the thickness of flow channel plane and red blood cell hematocrit. METHODS: A system with flow channel technique and light transmission measurements were applied to gaining red blood cell aggregation curve. RESULTS: The forming time of red blood cell aggregation body and the thickness of aggregation body as well as red blood cell hematocrit were linearily correlated with a correlation coefficient gamma of 0.989 and 0.990 respectively. CONCLUSION: When red blood cell aggregation process is studied using different methods, red blood cell aggregation time index can not be compared.