Abstract: There were a lot of records on the taboos of forest harvesting lunar month in ancient China. In order to fully understand the ancient people’s understanding of those taboos and their ground, the relevant documents in the ancient literature were extracted and classified to analyze the ground of determining taboo months and distinguish whether each month is suitable for harvesting. According to the study, the factors that determine months of forest harvesting in ancient China are mainly time, anti-mite condition, guarantee of wood property, yin and yang reconciliation, ease of construction, and guarantee of regeneration. Different factors lead to varied claims of the month of harvesting. Many months are both suitable and unsuitable which makes the problem of determining the harvesting month more complex, reflecting the diversity and comprehensiveness of the ancients in forest harvesting. In general, the ancients believed that harvesting was prohibited from January to March in the lunar calendar, while there was a different view on whether it is suitable for harvesting from April to September. Bamboo can be harvested from June to July and wood is suitable for harvesting from October to December.