To investigate the bacterial functional diversity regarding soil carbon metabolism in Sanjiang Plain wetlands, the top soils (0–20 cm) of three different land use types were collected in Sanjiang Plain, China. The distribution and variation of carbon source utilization was assessed by the Biolog microplate method. The results showed that the physicochemical properties of the soil were significantly different between the three land use types, wetland, farmland and forest (P < 0.05). The Average Well Color Development (AWCD) of all samples increased with incubation time, whereby the values of AWCD were highest in soil samples from wetland and lowest from forest. The soil bacterial diversity differed significantly between the three different soil types, and the McIntosh and Shannon-Wiener diversity index was significantly lower for forest soil. This shows that the bacterial community structures were influenced by soil physicochemical properties, with the AWCD and diversity index decreasing from wetlands to farmlands to forests. The utilization of six categories of carbon sources by soil bacteria showed significant differences for carbohydrates, polymers and carboxylic acids, but not for phenolic acids, amino acids and amines (P > 0.05). Principal component analysis (PCA) indicated that soil bacterial carbon utilization revealed obvious spatial variation, suggesting the bacterial metabolism diversity could be reflected in the use of carbohydrates, amino acids and carboxylic acids, particularly carbohydrates. In addition, soil physicochemical properties and vegetation composition were important factors modifying soil bacterial composition and functional activity in different land use types.