In order to solve the laying problem of the sand cushion on ultra-soft soil, and to decrease the cost in vacuum preloading projects because of the increasing price of the natural sand, the recyclable three dimensional drainage net made of polythene is used to replace the sand cushion. A comparison has been carried out between the sand cushion and the three dimensional drainage net when they act as horizontal drainage cushion. Field tests are conducted to verify the vacuum degree under the sealing film and the vertical drainage effectiveness of soil under the drainage net. The action mechanism, the laying method and the recyclable utilization method are studied in the tests. The tests results show that it is feasible to replace the sand cushion with geotechnical drainage net and this technology is more convenient and effective for the improvement of ultra-soft soil.