In this paper, the effects trace carbon element on microstructure and micro-hardness of a forged near beat titanium alloy through solution and aging treatment were studied. The results show that the addition of carbon element has a significant effect on the refinement of beta grain. Through solution treated at single field, the size of beta grains decreases from 137μm to 37μm and becomes more uniform with the increasing of carbon from 0 vol.% to 3 vol.%. And beta grains began to grow as the C content continued to increase. After aging treatment, the size and volume fraction of secondary alpha phase decreases with the increasing of carbon. Additionally, with the increasing of carbon, grain boundary alpha phase reduces gradually through single-aging treatment. Due to the influence of grain refinement, TiC particles and secondary alpha phase, with the increase of carbon, the micro-hardness of the alloy increased significantly under different heat treatment conditions.