The invention discloses a wind turbine generator system pivoting support gear tooth thickness measuring device which is used for measuring with a feeler gauge. The measuring device comprises a horizontal substrate. A protruding measurement calibrator is arranged at the middle part of the horizontal substrate. When measurement is carried out, the horizontal substrate is fixedly set the tooth top surface of two adjacent gear teeth, and the measurement calibrator stretches into the tooth pitch between two adjacent gear teeth. One side of the measurement calibrator contacts the tooth surface of one gear tooth. A measurement pitch is formed between the other side of the measurement calibrator and the tooth surface of the other gear tooth, so that the feeler gauge is inserted into the measurement pitch for measurement. The invention further discloses a measuring method based on the measuring device. The measuring device provided by the invention has the advantages of simple and compact structure, easy manufacture, convenient and fast operation, high measuring precision, and greatly improved measuring efficiency.