The rhizosphere soil of facility cucumber was selected to study the effect of different biological carbon contents on changing rule of nutrient content and bacterial communities, and the regulated mechanism between nutrient content and bacterial communities during fruit growth stage. The treatments were amount of 5t, 10t, 20t, 40t and 60t biological carbon respectively added in per hectare, and the test control was the soil which did not added biological carbon in the experiment. The results showed that the content of rhizosphere soil alkali hydrolysis nitrogen, available phosphorus, available potassium, organic carbon, total nitrogen content were improved in various degree with amount of 5~60t/hm2 of biological carbon, that bacteria abundance of Proteobacteria, Actinobacteria, Firmicutes were increased but bacteria abundance of Acidobacteria, Chloroflexi were reduced with amount of 20~60t/hm2 of biological carbon, that contents of soil alkali hydrolysis nitrogen, available phosphorus and available potassium were promoted improvement by biochar regulating and improving quantity and proportion of Proteobacteria Gammaproteobacteria and Actinobacteria Actinobacteria Actinomycetales. The study also showed that by comprehensive comparison, the effect of amount of 20t/hm2 of biological carbon was better than that of other treatments, and the treatment of amount of 20t/hm2 significantly and respectively increased rhizosphere soil alkaline nitrogen content by 39.86%, available phosphorus content by 135.95%, available potassium content by 81.35%, organic carbon content by 82.89%, and total nitrogen content by 73.77%, compared with the test control in full fruiting period of cucumber.