Abstract: The collodion embedding and section making method is one of the important techniques in microscopic research of biology.This method has unique advantages in making high quality sections especially when the specimens are large in scale,the hardness is too high or too low and the production of thick slices.Based on the authors’ practical experience,this article introduces the principle,operation flow and technical points of the cotton wool embedding method,and shows the results and advantages of the method under the above three conditions.Practice shows that is a good method when deals with these particularly large size,high hardness or very low specimens,or slices both large thickness and fine structure.