The invention discloses a method of freezing, concentrating and treating saline wastewater. The method comprises the following steps: saline wastewater to be treated and a cooling agent are conveyed into a crystallizer to obtain a concentration solution of saline wastewater and solid ice crystals after heat transfer, and a part of the concentration solution of saline wastewater is expelled from the system; the solid ice crystals containing the concentration solution of saline wastewater are put into a solid-liquid separator to separate solid from liquid and the treated solid ice crystals are washed with water and put in an ice-melting jar to obtain chilled water after melting. The preparation method can achieve continuous operation at normal pressure or low pressure condition and is low in the requirement for devices; the cooling agent and the saline wastewater are in direct contact to transfer heat, so that the heat transfer efficiency is improved, the device size is effectively decreased and scale production can be achieved; according to technological requirements, saline water can be concentrated into different concentration levels, so that the treatment scale of the follow-up technologies is significantly decreased and the preparation method is good in adaptability; the preparation method is wide in application range and can be widely used in chemical industry (such as gasifier black water and wastewater treatment, and the like), sea water desalination, and the like.