Abstract: In the roof garden, Zephyranthes candida Herb and S.Lineare were made as target plants, each kind of the plant was separated into two groups: One group was planted in the culture material with certain quantity Sepiolite added in, the other was planted in the same culture material but with no Sepiolite. 90 days later, the growth of the two group plants were compared, the results shows: Plants in the culture material with Sepiolite added in grew much more better. But the Sepiolite made it difficult to let the rain water seep into the culture material when it’s raining hard, the light part of the culture material was easy to be flooded away. So, when the roof was a slanting one, the Sepiolite could not be added into too much.