Abstract: With the replacement of glazing material by plastic, more and more attention has been paid to the water drop problem in the greenhouse. Now, a lot of anti-drop plastic films and rigid plastic sheets are available in the market, which can be used to improve the light conditions in greenhouses. However, the checking criteria for the anti-drop material vary from place to place in the world, which makes it difficult for greenhouse growers to select glazing material. In this paper, the principles and practicability of several anti-drop detection methods were analyzed. It was found that in most of the detection methods the test material is horizontally placed according to greenhouse conditions, the anti-dry property of glazing materials should be detected at a slope, as the roof and walls of the greenhouse are not horizontal and the anti-drop property has a great difference between slope and horizontal conditions. Thus a new method by calculating the area ratio of water drops on a 15°～30° slope plastic material was put forward and the area ratio of water drop was less than 10% for the plastic with anti-drop property in a series of tests in plastic films and PC sheets, which is expected to be able to provide basis and standard for evaluating the anti-drop property of glazing material.