In order to improve the efficiency of aluminum foil defect detection in medicine bubble wrap, a new aluminum foil defect detection method based on four-light photometric stereo method was proposed. The surface gradient information of the object under test was obtained efficiently and accurately using four-light photometric stereo method. The gradient information of the object under test was used to get the surface Gaussian curvature, which was then treated by morphology processing. Finally from the gray image, aluminum foil defect area was segmented effectively. The experimental results showed that this method could effectively detect aluminum foil defects, the accuracy of defect detection was above 91%.