The ink unearthed from the Warring States tomb M56 of Jiudian village, Jiangling County in Hubei province provides important material objects for researching the early ink materials and technologies in China. However, the types of ink, additives and binding media in ancient ink are still unknown. In this paper, Infrared Spectrometer (FTIR), Transmission Electron Microscopy (TEM), and Pyrolysis-Gas Chromatography/Mass Spectrometry (Py-GC/MS) were used to analyze the morphology and chemical composition of the Warring States ink. The results show: (1) the FTIR analysis reveals that there are the vibration absorption peaks of soot C=C skeleton near 1 595 cm^-1, carboxylic acid carbonyl C=O (1 716 cm^-1), alcohol C—O (1 031 and 1 092 cm^-1) bonds, and O—H (3 421 cm^-1) in OH and COOH, which indicates that there are carboxylic acids and alcohol in the Warring States ink; (2) the TEM results show that the characteristic of Warring States ink is similar to pine wood soot ink; (3) the results of Py-GC/MS show that there are a series of polycyclic aromatic hydrocarbons (PAHs), pyrolysis compounds of pine wood (retene and methyl dehydroabietate), camphor and cedar oil-related aromatic compounds (cedr-8-ene, beta-cedrene, cuparene and cedrol). Among these, the content of PAHs and the characteristic compounds of pine wood indicates that the Warring States ink is pine wood soot ink. Besides, camphor and cedar oil are used as additives in Warring States ink. This study shows that camphor and cedar oil existed in pine wood soot ink as additives during the Warring States period in China.