Gel films were prepared from the mixtures of ultra-high molecular weight polyethylene(UHME PE) and high density polyethylene (HDPE) in a decalin solution. To investigate the formation of mixed crystals in the blends, i.e.cocrystallization, melting behaviors of the gel films and the slowly cooled films from melt were analyzed by differential scanning calorimetry. The slowly cooled films from melt as well as gel films showed the single melting peaks and this was ascribed to the formation of mixed crystals. The heat of fusion of the slowly cooled films from melt was nearly linear to the weight percent of UHMW PE and HDPE but gel films showed a minimum value. However, no significant lattice changes were found in the X-ray diffraction of gel films. The tensile moduli of gel films decreased with the increase of weight percent of HDPE and the yield stresses were almost constant in the intermediate weight percent of UHMW PE and HDPE.