Taking the Changshu region of Jiangsu Province for an example,through analysis on drainage modes of rainwater in low-lying field,the existing problems in conventional design method for flooded fields drainage were put forward,and the conception and method for pressure rainwater pipe design were discussed as well.

In order to improve the water drainage reliability of the rainwater pipeline,the reliability theory of engineering structure is introduced into rainwater pipeline.

This paper submit some methods of rainwater pipeline combining with geography feature, such as the pipe diameter determination and pipeline embed are conducted separately, hydraulic calculation adopts unitary hydraulic gradient, the pipeline embed adopts unitary setter slope, advocating plain joint and spout covering and so on.

The structure and function of the intelligence system for storm sewer design are described.

Presently, regarding the design of storm sewer, many designed departments still adopt the method of consulting the chart for hydraulic calculation, this computational method depends on experience, low precision , time-consuming, and unfavourably optimizating the design.

During modifying urban combined sewer into separated sewers,the urban combined sewer can be locally or totally retained as storm sewer on favorable conditions and new wastewater sewer can be built.