The testing method for a polarizing plate includes the following two types of testing: a selected light beam passing through a filter, a polarizer, a concave lens and a filter, a mirror, a concave lens and finally to a sample of a polarizing plate; the sample is rotated along z-axis to ascertain that if there is any variation of shade in an optical domain, in order to differentiate defective samples from qualified ones. By applying the method, gooseflesh in the sample is ascertained by naked eyes easily while feeding; the checking result can be reflected to a factory owner. The test cost is low and requires only inexpensive instruments. Moreover, an additional processing of polarizing plate is needless.