Abstract: An efficient and precise measuring method of linearity of photodiode andphotomultiplier is described in which the output signals of a standard tube and atest tube with the same frequency and phase are X-Y displayed on the oscilloscope,with the specially made xenon lamp as the light generator. Current stabilizing system with double-trolley helipots, cooperated adjustmentand two sets of current measuring equipment are used to improve the adjustmentof operational behaviour of the photomultiplier.