Horse manure (HM), which is a crucial waste material from livestock sector in Thailand. It consists of hemicellulose, cellulose and lignin that has a potential for carbon material production. In this research, carbon material was prepared from horse manure by hydrothermal treatment (HT) at 200ºC for 24 h with improvement of porosity and surface structure by acid catalyst that gif.latex?HNO_{3}, gif.latex?H_{2}SO_{4}, HCl and gif.latex?H_{3}PO_{4}with ratio of 1, 3 and 5 wt%, respectively. Then, HT char was pyrolysed at 300ºC for 2 h to obtain the carbon nanomaterial. SEM image displayed that HCl catalyst shows highest porosity on char surface. The production yield treated by HCl 5 wt% is approximately 51.44 wt%. FTIR spectrum confirm that the functional group of biomass polymer was decomposed.