Low elevation green land is an effective measure to relief city flood discharge pressure and to reducerunoff losses caused by the establishment of a large amount of real estates.By calculation of runoff yield andflow concentration,the rainwater storage capacity of different green lands with various depths in Beijing Citywas analyzed.Approximately 80%of the rain with 2-year re-occurrence probability could be sequestrated ifthe green land ratio was higher than 20% with concave depth of 15cm as specified by the requirements realestate development in Beijing City.With a concave depth of 20cm,the sequestration rate could be still higher than 80%for the rains with 5-year re-occurrence probability.Based on the earthwork balance,the calculation method for digging depth of low elevation green land was proposed.According to the calculation andanalysis,the design depth should range between 15～20cm with digging depth of 6～15cm for low elevationgreen lands.