During the imperial power shift from Emperor Taizu to Emperor Taizong in the Song Dynasty, there was an important while mysterious event of "ZHANG Shou-zhen's meeting with the immortal descending from heaven", in which the occultist ZHANG took the advantage of people's black fiend worship to help Taizong to take the crown. By comparing different historical texts such as official National History, Authentic Records, novels and religious texts, this paper examines the differences and similarities of these texts, probes into the details and finds out that Emperor Taizong had plotted for a long time to get to the throne. ZHANG was an occultist deeply involved in the royal power strife. Though having a high position during the reign of Emperor Taizong, he was also deeply mistrusted by Taizong. When considering the shift of the imperial power in his old age, Taizong finally poisoned ZHANG as an uncontrollable factor.