The invention discloses a photomultiplier tube homogeneity testing system and method based on a galvanometer. The testing system comprises a light source, a collimator, a diaphragm, an optical filter, the galvanometer and a computer. The galvanometer comprises two opposite reflectors. A computer is used for controlling the angles of the two reflectors so that the reflection angles of light beams passing through the reflectors can be controlled, the light beams reflected by one reflector scan in one direction, the scanning directions of the two reflectors are perpendicular to each other, and therefore two-dimensional scanning of the surface of a PMT can be finished through cooperation of the two reflectors. According to the system, no connecting lines exist in a light path, setting up is easy to carry out, and a position is easy to correct; the PMT is easy to replace, and the homogeneity of a large number of PMTs can be tested; the control precision of the galvanometer is high, precise displacement of the light beams on the PMT can be ensured, and each effective detection unit of the surface of the PMT can be traversed; by selecting different optical filter types, the system can be widely used for testing the homogeneity of the PMTs with different wave lengths.