The invention relates to a positioning device of a glass edge grinding machine. The problem that large-range adjustment and positioning cannot be achieved in the prior art is mainly solved. An adjusting flat plate is arranged on a support plate, the adjusting flat plate, a positioning plate, a positioning synchronization belt, a driving wheel, a driven wheel, a tensioning wheel and a bevel gear group form an integral structure, and integral displacement is adjusted through bolts. The positioning device of the glass edge grinding machine is reasonable and compact in structure, reliable and easy to operate and convenient to use and adjust. Parts are independently installed respectively and can be operated in a unified mode, and the demands for large-range adjustment and positioning and power delivery are effectively met.