Wastewater treatment technology of constructed wetland is becoming more and more popular all over the world for its good effect, low investment, simple operation, and so on. This paper mainly discusses the purification mechanism of constructed wetlands and their development status at home and abroad, comparing the advantages and disadvantages of constructed wetlands and natural freezing sewage treatment technology, it puts forward the idea about developing a feasible comprehensive system which is the integration of constructed wetlands and natural freezing sewage treatment technologies and uses this system in coastal saline-alkali area of the northern China.