In order to conquer the depth of field limitation in underwater range-gated imaging, the advantages of laser radar imaging theory and images reconstruction are taken, considering the reality of our laboratory, range information acquisition process of underwater range gated serial images is analyzed in detail. In view of the characteristics of range gated images obtained in different quality water, subtracting background image from object image, choosing maximum layer progressive reconstruction among adjacent images according to period plus tiny time offset and reconstruction after segmentation are used to images. Serial scene “slices” in different range is attained to testify the proposed algorithm. An image comprising objects in all “slices” from 8.2 to 13.2 m is reconstructed. In order to explain the range information in the reconstructed image, a pseudo color image is reconstructed by three adjacent images containing range information from 10.7 to 13.2 m.