The present invention provides an optical distance measuring method, comprising confirming an expression of a first measured distance according to a plurality of first parameters; computing a time-of-flight (ToF) measured distance according to a time of flight; computing optimized values of the plurality of first parameters and an optimized value of a ToF error corresponding to the ToF measured distance according to the expression of the first measured distance and the ToF measured distance; and obtaining a depth image information according to the ToF measured distance, the optimized values of the plurality of first parameters and the optimized value of the ToF error; wherein the plurality of first parameters comprises an elevation angle and an Azimuth angle corresponding to the object reflecting point and a distance between the light emitting module and the light sensing module.