KDP crystals with different concentration of EDTA in solution were grown;light scatter was detected with laser scanning technique.It has been proved that light scatter in KDP crystal aggravated with the increasing concentration of EDTA in growth solution for EDTA inhibited the growth of KDP crystal at high concentration,thus mother liquid inclusions formed,which cause light scatter.And the light scatter in KDP varied within different sector of KDP crystal.The effect mechanism was discussed.