With the increasing exploration and development of deep and ultra-deep wells， harsh conditions such as high temperature and high pressure put forward higher requirements for drilling fluid. In view of the difficulty of conventional wellbore strengthening materials to meet the high temperature and high pressure in ultra-deep drilling process， research has been conducted on a graphite material which can expand at 150℃， and its characteristics of plugging and fluid loss reduction in high temperature drilling fluid have also been explored. Expanded graphite is a kind of flexible expansion material with high temperature resistance （500℃）， high expansion performance and self-lubricating property. The initial expansion temperature of the existing expanded graphite is generally higher than 300℃， and cannot expand at the bottomhole temperature. The multi-component oxidation intercalation method was used to prepare the expanded graphite material with initial expansion temperature reduced from 300℃ to 150℃. The expansion mechanism of the multi-component oxidation intercalation is examined， and its plugging and filtration performance in high temperature drilling fluid is further investigated.