Three sesquiterpene ortho-naphthoquinones were isolated from the methanolic extract of root bark of Ulmus davidiana Planch whose stem and root bark have been used as an oriental medicine for the treatment of edema, mastitis, gastric cancer and inflammation. The structures of these compounds were established on the basis of spectral data obtained from UV-vis, IR, HR-EIMS and NMR spectrometry, including the pulse field gradient (PFG)-HMQC and HMBC techniques. Their structures were determined as 2,3-dihydro-3,6,9-trimethylnaphtho(1,8-b,c)pyran-7,8-dione, 3,6,9-trimethylnaphtho(1,8-b,c)pyran-7,8-dione and 2,3-dihydro-4-hedroxy-3,6, 9-trimethylnaphtho(1,8-b,c)pyran-7,8-dione, which were identified as mansonones E. F and H, respectively. These compounds have originally been isolated from Mansonia altissima Chev, but have never been isolated from Ulmus davidiana Planch. Especially, mansonone H was isolated for the first time from Ulmaceae. The mismatched carbon chemical shifts of mansonones E and F in the reported literature were corrected by the aid of the PFG-HMBC spectral data.