We have investigated the effects of the stretching time on the microporous alumina filled HDPE films. The alumina filled HDPE films were uni-axially stretched up to 600% in a propylene glycol bath at 100 ℃ with different stretching time. As the stretching time increased the porosity of the alumina filled HDPE membrane was increased. The crystallinity of the alumina filled HDPE membrane were increased steadily with an increalsing stretching time. However, the tensile strength was decreased with an increasing stretching time due to the increased pores.