The invention relates to a test platform for an absolute grating ruler. The test platform for the absolute grating ruler comprises a complementary metal oxide semiconductor (COMS) sensor, an optical focusing mirror, a COMS eye lens, a collimated light source, a grating ruler supporter, a double-grating-strip grating ruler, a grating ruler supporter, a mobile platform, a linear slide rail, a linear propulsion system, a stepping motor and a base, wherein a linear movement system is composed of the stepping motor, the linear propulsion system and the linear slide rail, and a sampling system of image processing is composed of the COMS sensor, the optical focusing mirror, the COMS eye lens, the collimated light source and the double-grating-strip grating ruler. According to the test platform and the test method for the absolute grating ruler, accuracy and reliability of encoding measurement are improved, so that accurate positioning can be achieved. The test platform for the absolute grating ruler has the advantages of high accuracy, high controllability and high reliability. The invention aims at providing a method for the absolute grating ruler of double encoding strips with optical amplification. In addition, through reasonable and reliable image analysis and closed-loop control, mobility, reliability and accuracy of the grating ruler are enabled to be greatly improved.