He was a son of Emperor Wen and his powerful wife Empress Dugu, and during most of his father's reign was given great control over the modern Sichuan and Chongqing region.
In 592, Yang Xiu appeared to be briefly recalled to the capital Daxing to serve as the head of the legislative branch of government, the Neishi Sheng (內史省), when Emperor Wen put him and the official Yu Qingze (虞慶則) in charge of investigating claims that the deputy head of the executive branch, the Shangshu Sheng (尚書省), Su Wei, had been engaging in factionalism.
Over the years, as Yang Xiu became more and more accustomed to ruling over the region and grew arrogant and wasteful beyond the appropriate levels for an imperial prince.
[2][4] In fall 602, Emperor Wen summoned Yang Xiu back to the capital, sending the general Dugu Jie (獨孤楷) to replace him.
Yang Xiu considered refusing to return to Daxing, but decided not to resist after being advised by Yuan Shimin (源師民) otherwise.
When Yang Xiu arrived at Chang'an some three months after his departure from Yi Province, Emperor Wen refused to say anything to him while meeting him.
Around the new year 603, Emperor Wen reduced Yang Xiu to commoner rank and put him under house arrest within the Bureau of Eunuchs, not permitting him to meet with his wife and children.
Further incensed by the petition, Emperor Wen issued an edict accusing Yang Xiu of 10 crimes, particularly stating, "I do not know what kind of relatives 'Yang Jian' and 'Yang Liang' are to you."