The invention provides a rock weathering speed measurement method. The rock weathering speed measurement method comprises the steps of firstly discovering microscopic weathering characteristics in the initial rock weathering stage, namely the natural phenomenon that microcracks formed in fracture planes after rock failure continuously extend in rocks, and definitely defining the starting and stopping points and the starting and stopping time of the rock weathering. As for microscopic weathering characteristics, the rock weathering speed measurement method can carry out quantitative measurement on the width of the microcracks (namely, the rock weathering depth) by adopting a microscopic observation technology, a camera shooting technology and an image processing technology, and solves the technological problem that the microscopic weathering characteristics are invisible to the naked eyes. The rock weathering speed measurement method can record the rock cracking time by utilizing human activity events or geological events, determine the starting time of the weathering, and solve the technical problem that the weathering simulation time is hard to prolong to more than ten years. The rock weathering speed measurement method has the advantages of easiness in operation and accuracy in measurement results.