The problem of hole-wall stability includes the well collapsing and the well fracture. The formation of ultra-deep scientific drilling (UDSD) is provided with high stress, high temperature and high formation pressure. The hole-wall stability of UDSD is one of the focuses. Take the example of 12000m UDSD, starting from the formation temperature, analysis was made on the changes of equivalent static density of drilling fluid and annular pressure equivalent density caused by drilling fluid circulating temperature, and on the influence to hole-wall stability by formation temperature-gradient stress and formation temperature-difference stress.