This study aims to compare the knee morphological difference between Han and Mongolian Chinese in China. This will improve the knee prostheses design. A total of 37 natural knees of Han Chinese (13 males, 9 females) and Mongolian Chinese (8 males, 7 females) were measured used Mimics medical imaging program, and the parameters included fML (the femoral mediolateral length), fLAP (the femoral lateral condyle anteroposterior length), fMAP (the femoral medial condyle anteroposteriorlength), tML (The tibial mediolateral length ), tLAP (The tibial lateral anteroposteriorlength) and tMAP (the tibial medial anteroposterior length), The aspect ratio (defined as fML/fAP and tML/tAP;). The sizes of femur and tibia of the males were larger than those of the female for Han Chinese (IML, fLAP and fMAP) mean +/- standard deviation: 84.57 +/- 4.70 vs.76.52 +/- 3.56, 65.75 +/- 2.70 vs. 60.53 +/- 3.81 and 67.10 +/- 3.67vs. 62.1 2 +/- 3.55; tML, tLAP and tMAP: 74.68 +/- 4.27 vs. 65.82 +/- 3.51, 36.13 +/- 2.96 vs. 31.12 +/- 2.91 and 44.54 +/- 3.02 vs. 40.11 +/- 3.80 and Mongolian Chinese (fML, fLAP and fMAP) : 88.20 +/- 4.57 vs. 77.92 +/- 2.97, 68.82 +/- 4.22 vs. 61.31 +/- 1.92 and 69.81 +/- 3.53 vs. 62.13 +/- 1.63; tML, tLAP and tMAP: 78.00 +/- 3.80 vs. 66.71 +/- 3.52, 40.17 +/- 3.09 vs. 32.91 +/- 1.68 and 48.65 +/- 3.00 vs. 41.97 +/- 2.48). The aspect ratio of the knee in Mongolian Chinese was smaller than those ofHan Chinese (liML/fAP:1.28 +/- 0.04 vs.1.29 +/- 0.03 for males;1.27 +/- 0.04 vs.1.27 +/- 0.05; tML/tAP: 1.60 +/- 0.04 vs. 1.68 +/- 0.10 for the males, 1.59 +/- 0.13 vs. 1.65 +/- 0.10 for the females). The effects of nationality and sex on the size and shape of knee were significant (p<0.05). The results suggest that an anatomic matched knee prosthesis should be taken into account different nationalities even in the same race.