Disclosed are a method and system for optical calibration of a 3D printer. The method includes: projecting, by an optical apparatus, a projection image to a projection platform, placing a calibration plate on the projection platform, and capturing the projection platform; identifying the coordinates of calibration points and the coordinates of actual projection points according to the captured image to obtain a matrix of calibration points and a matrix of actual projection points; rotating and translating the matrix of the calibration points and/or the matrix of the actual projection points, and calculating a distance value T0 between the calibration points and the actual projection points in an image coordinate system; converting the T0 in the image coordinate system into an offset C1 in a pixel coordinate system, and inversely distorting an initial ideal projection image according to the offset C1 to offset optical distortion.