A new method to make computer generated rainbow hologram using look-table is proposed.According to the relation of object point position with its line-element hologram,an object light distribution data table is established.This data table contains the line-element hologram′s object light digital distribution of all possible object points. For any actual objects,its all sample points′ light distribution can be obtained by looking the data table.Adding all the sample points′ light distribution,the actual object′s light distribution can be got.Computer-generated rain-bow hologram can be made by calculating interference fringe of the object light distribution and of reference light.This method well utilizes the characters of line-element hologram to increase computing speed.