Sewage sludge production is increasing greatly in China with the development of municipal wastewater treatment, and agricultural application of municipal sewage sludge (MSS) has become one of the main outlets for MSS worldwide. However, direct application of MSS and its composts to agricultural lands can lead to heavy metal contamination of soil and food. Accordingly, application of MSS to plants that are not used for food is a better alternative. Therefore, this study was conducted to investigate the use of the hybrid giant napier (Pennisetum hydridum), which has a large biomass and can serve as animal feed or paper-making materials, to efficiently produce plant biomass while degrading MSS. To accomplish this, a field experiment composed of small plots with four treatments, soil, fresh sludge, soil-sludge mixture at a ratio of 1:1, and phyto-treated sludge, was conducted. Additionally, Giant Napier were cultivated following transplantation of ramets with roots or direct planting of cut stems. MSS was acquired from the Datansha Wastewater Treatment Plant in Guangzhou, placed in plots with a height of 20 cm on the ground and covered with permeable plastic nets. The survival and growth rate of the Giant Napier were then followed and the main characteristics of the sludge were investigated. A pot experiment and a field experiment were also conducted to investigate the feasibility of transplanting hybrid Giant Napier directly into fresh MSS using seedlings generated from stem cuttings in normal growth medium. The results showed that the hybrid Giant Napier could not survive directly in fresh MSS when cultivated from stem cuttings, as indicated by a survival rate of only 16.67%, even when transplanted ramets with roots were included in the plot. However, the plants survived and grew well in the soil-sludge mixture and phyto-treated sludge. The survival rates of stem cuttings planted in the soil-sludge mixture and phyto-treated sludge were 58.33% and 75.00%, respectively, and the yield of biomass of these two treatments ranged from 19.80 t/hm² to 22.20 t/hm² on a dry weight basis over two months, which was 4.55 to 5.11 times higher than that of the soil only treatment. Additionally, the hybrid Giant Napier absorbed K well, as indicated by the K content in the plant biomass reaching about 40 g/kg on a dry weight basis in the three sludge treatments. The total N, P₂O₅ and K₂O content also reached 70 g/kg, indicating that the harvested plant biomass can be used as organic potassium fertilizer. The levels of Cu, Zn, Pb and Cd in the hybrid giant napier were below the tolerance limits of heavy metals according to the Chinese standards of feeds (GB 13078-2001), indicating that the produced biomass was safe for use as animal feed. The pot experiment and field experiment showed that the survival rate of the hybrid Giant Napier transplanted into fresh MSS with seedlings generated from stem cuttings in normal growth medium reached more than 66.67% and the plants grew to an average of 2.6 m after 6 months. Overall, the results of this study indicate that the hybrid Giant Napier can be directly planted in fresh MSS and produce a high yield.