Abstract: In the literatures of the Tang and Song Dynasties,the records of the historical event of the first visit to Yangzhou by Emperor Yang Guang of the Sui Dynasty in the early years of Daye era (605-616) are too against common sense.Among them,the figure of tens of thousands of royal luxury pleasure boats,including dragon boats,manufactured in Yangzhou in just over five months,is more than ten times the annual shipbuilding capacity of the Northern Song Dynasty.The dragon boat is an extra-large pleasure boat (with many decks) and cannot be used as a long-distance shipping tool.Moreover,during the Sui and Tang Dynasties,the transportation route from Luoyang to Yangzhou,consisting of the Yellow River,Bianshui Canal,Huaihe River and Shanyangdu Canal,was impassable to giant boats at all.The record of Emperor Yang Guang's fleet of dragon boats originated from Du Bao's Daye Zaji.On the one hand,in ancient China,political scholars from later dynasties were accustomed to discrediting the previous emperors and exaggerating their extravagance and debauchery,especially towards the last monarchs.On the other hand,Daye Zaji is essentially a novel and cannot be used as a reliable historical resource.Sima Guang's Zizhi Tongjian with the aim of serving the monarchy of the Song Dynasty,extensively transcribing the absurd statements in Daye Zaji,thus causing these extremely glaring historical fallacies to spread for more than one thousand years.

Key words: Emperor Yang Guang of the Sui Dynasty, the Tongji Canal (Bianshui), the Shanyangdu Canal, dragon boat, Daye Zaji, Zizhi Tongjian