To explore contributions of microbial necromass carbon (MNC) to soil organic carbon (SOC) fractions under different artificial forest types, Robinia pseudoacacia, Armeniaca sibirica, and Pinus tabuliformis plantations on the Loess Plateau were selected as the study objectives. Then contributions of fungal necromass carbon (FNC), bacterial necromass carbon (BNC), and MNC to particulate organic carbon (POC) and mineral-associated organic carbon (MAOC) at 0—60 cm soil layers as well as its influencing factors under three artificial forest types were analyzed. Results showed that (1) contents of BNC, FNC, and MNC in POC and MAOC degraded with increasing of the soil layer depth under three types of artificial forest. (2) Contributions of MNC to MAOC accumulation under Robinia pseudoacacia and Armeniaca sibirica plantations were 60.9% and 52.0%, which were higher than that of POC (33.5% and 49.5%). The contributions of FNC to MAOC accumulation were 4.4 and 2.5 times that of BNC. For the Pinus tabuliformis plantation, contribution of MNC to POC accumulation at 0—10 cm soil layer was 73.8%, which was higher than that of MAOC (48.2%). And contribution of FNC to POC accumulation was 3.5 times that of BNC. However, at 10—60 cm soil layer, contribution of MNC to MAOC accumulation was 30.9%, which was higher than that of POC (24.4%). And contribution of FNC to MAOC accumulation was 3.4 times that of BNC. (3) There existed significantly positive correlations between SOC, total nitrogen contents and MNC/POC, MNC/MAOC (P ＜ 0.05). Clay content was positively correlated with MNC/MAOC significantly (P ＜ 0.05). However, pH value and sand content were negatively correlated with MNC/MAOC significantly (P ＜ 0.05). These results suggested that on the Loess Plateau, MNC at 0—60 cm soil layers mainly contributed to MAOC accumulation under three types of plantations, except for that in Pinus tabuliformis plantation at 0—10 cm soil layer. Compared to BNC, contribution of FNC to SOC fractions accumulation was higher. Contents of SOC, total nitrogen, clay, and sand as well as pH value were the major factors to affect contributions of MNC to SOC fractions accumulation.