Abstract: Since the energy distribution of the optical spot has great impact on the imaging quality in the microimaging with the filtering method of nondiffracting beam, the energy distribution of the weak imaging spot must be measured accurately. In the experiment, the light spots were measured by the scanning method. A pinhole attached to the flexure hinge mechanism was used to implement the 2-D scanning of the imaging spot accurately with a very small step, and the sampled light signal passing through the pinhole was received by a photomultiplier tube. Then the signal was transferred to a computer for the further processing after it was processed by the low noise current-to-voltage conversion and amplification circuits. Finally the energy distribution of the spot was reconverted and obtained through computer processing of the measurement data. The result was given in three dimension energy profile after the actual weak light spots were measured by the selfmade device. This method can be used to accurately measure the energy distribution of irregular small weak spots.