Abstract：The 42nd Difficult Issue in the Nan Jing （the Classic of Difficult Issues） is an important chapter on ancient human visceral anatomy. By interpreting the visceral anatomy records in the Nan Jing using modern units of measurement and comparing them with modern anatomical results， this study finds the correspondence between the organs described in the Nan Jing and those in modern anatomy. It also speculates on the reasons for the differences observed. The comparison reveals significant discrepancies between ancient and modern measurements of the gastrointestinal tract and bladder， while the other visceral structures show a general consistency between ancient and modern data.