In this paper, composting technology was used to treat agricultural waste chicken manure. The dynamic changes of the relative amount, chemical, optical and thermal properties of humic acid during the composting process were systematically studied. The results showed that the relative amount of humic acid increased from 5.46% to 8.36% with the ratio of H/C decreased and the condensation degree of humic acid molecule increased. In the infrared spectrum of humic acid, the integral area ratio of aromatic absorption peak to aliphatic absorption peak decreased from 0.51 to 0.14, and the lgK also decreased, it indicated that composting treatment was beneficial to the decomposition of simple compounds and the formation of complex organic matter in chicken manure. However, after 30 days of composting treatment, the lgK decreased to 0.85, which was still higher than that in farming soil, i.e., the molecular structure of humic acid in chicken manure treated by composting still has potential for further stabilization. Differential thermal analysis showed that the Peak Exothermic Temperature and weight loss all increased with the increase of composting time of chicken manure, which indicates that the molecular structure of humic acid in chicken manure became more complex and the degree of humification was obvious. Therefore, composting treatment can not only increase the relative amount of humic acid in organic materials but also improve the quality of humic acid.