The influence of residues of green manure (AV) on Carbon (C) of soil microbial biomass (BMS) corresponding to an area of livestock use (livestock) was evaluated. The study was developed in the Livestock and Soil Project of the Tropical Agricultural Research Center (CIAT) Santa Cruz, Bolivia; The experimental design was completely randomized, with 6 treatments and 4 repetitions. The evaluation of the BMS was 30 days after the incorporation of the residues of the five legume species used as AV being black Mucuna (Stizolobium aterrinum), Lab lab (Lablab purpureus), Mucuna ash (Stizolobium niveum), Crotalaria (Crotalaria juncea), pork bean (Canavalia ensiformis) and as a control (spontaneous vegetation) with the irradiation and incubation method. It was found that the AV species have the highest concentration of C-BMS with respect to the control, and among the AV the species of creeping habit are those that concentrate the highest C in their BM.