In the design of cofferdam section，the stability of the cofferdam body is usually considered as only the internal filling sand，which will lead to the design of the cofferdam section is not economical and extend the construction period. At present，there is no relevant code in China to guide the stability calculation of geotextile cofferdam considering the effect of bag reinforcement. In view of this problem，by analyzing the reinforcement effect of geotextile and using the method of calculating the geotextile reinforcement effect of reinforced structures abroad for reference，a calculation method is proposed to consider the reinforcement effect of the bag cloth by checking whether the maximum resistance provided by the bag cloth satisfies its allowable tensile strength. The practice shows that this method can optimize the section of cofferdam body，shorten the construction period and save the investment.