This paper reports the relationship between ultra-drawing and chain formation with gauche conformation in ultrahigh molecular weight polyethylene (UHMWPE) gel-films, which were prepared under several different concentrations, measured by infrared analysis. We demonstrated the effect of concentration distribution of gauche conformation on the ultra-drawing of UHMWPE gel-films. The relationship between the concentration distribution of gauche conformation and chain entanglement is also discussed here. It was found that the concentration of gauche conformation, defined by IR intensity ratio: sigma = I-1303/I-1352, increased as the film-casting concentration increased. The UHMWPE gel-film prepared from the solution around the critical concentration (400-500 kg/m(3)) showed the highest draw ratio (lambda > 300). The changes of gauche conformation concentration correspond to that of chain entanglement number deduced by Matuso from specific viscosity. The sigma value of UHMWPE gel-films decreased to a constant one after heat treatment. The heat treatment temperature affected the sigma value more than the heat treatment time did. The sigma value remained unchanged after heating the sample for 5 min at the drawing temperature. These results are consistent with the hypothesis that annealing at the drawing temperature is a prerequisite stage to reach ultrahigh draw ratio (Spells and Hill, Polymer32 (1991) 2716). The UHMWPE gel-films could easily reach ultra-drawing (lambda > 300) when they were drawn in the range of low sigma values. These results were of great importance to detect and design the preparation conditions of UHMWPE gel-films deeply, the relationship between ultra-drawing and the structure texture and to ensure the ideal orientation of molecular chains.