Introduced from Africa by Fujian Agriculture and Forestry University in 2005, the Giant Juncao ( Pennisetum sp.) had the features of tall, erect, forested with the high annual output of 200-400 t/hm². The crude protein content of the Giant Juncao was 10.8% after growth for 4 weeks, indicating the advantage of developed root system, strong stress resistance and quick growth variety. The Giant Juncao may be used to produce mushroom, fungi forage and forage additives successfully. Now, the Giant Juncao is used to control soil erosion and improve the soil properties. This paper studied the effects of the Giant Juncao on the soil microbial community functional diversity and fertility with different growth years (1, 2, 3 and 5 years) planted in the barren hillside. The results indicated that the utilization of carbon sources by soil microbes increased when culture time prolonged. The most obvious change happened in the culture time of 72-96 h. AWCD (Average Well Color Development) value reached the maximum in the culture time of 144 h. Generally, the order of AWCD value was 2 years> 3 years > 1 year > 5 years> CK. The values of AWCD of the Giant Juncao with different growth year was significantly higher than CK. AWCD was highest when the growth year of the Giant Juncao was 2 years, follow by 3 years. The difference of AWCD between 1 and 5 years was not significant. The principal component in the utilization of carbon source by soil microbes in the growth time of 96 h was analyzed. The results showed that the 8 principal components extracted from 31 carbon source were related to soil microbial carbon source utilization, the 1-8 principal components account for 25.39%, 18.89%, 11.28%, 9.31%, 6.84%, 5.60%, 5.26%, 5.60% of variables variance respectively, and account for 87.27% of the total variables variance. The principal component 1 and 2 could be used to distinguish the characteristics of soil microbial community with different growth years of Giant Juncao. The diversity of soil microbial community of the 2 and 3 years' Giant Juncao was significantly different with CK. The Shannon (H), Evenness and Brillouin indexes of soil microbial community with different growth time of Giant Juncao were significantly higher than CK. The Shannon (H), Evenness and Brillouin indexes of soil microbial community planted with Giant Juncao between 2 and 3 years, 1 and 5 years had no significant differences. Generally, pH value, organic matter, alkali solution nitrogen, effective phosphorus and rapidly-available potassium contents of soil planted with Giant Juncao were higher than CK. The content of organic matter of soil planted with 3 years old Giant Juncao was higher than CK by 98.20%. The content of alkaline hydrolysis nitrogen of soil planted with 5 years old Giant Juncao was higher than CK by 93.2%. The organic matter and alkali solution content of soil planted with 2, 3 and 5 years old Giant Juncao were significantly different to CK. The Giant Juncao planted in barren hillside could enhance soil microbial community functional diversity and improve soil fertility to a certain extent. Planting Giant Juncao in the Barren Hillside had certain positive ecological effect.