"China is a staunch defender of cybersecurity. It is also a victim of hacking," he said.
"The Chinese government will not in whatever form engage in commercial theft or encourage or support such attempts by anyone."
Xi - under pressure from Washington to take action against alleged Chinese groups stealing secrets and intellectual property of US companies - said China is ready to set up a "high-level joint dialogue mechanism" with the US on fighting cyber crime.
But, in an apparent response to US threats to apply punitive sanctions on Chinese officials, Xi said cyber theft is a crime that needs to be prosecuted in courts.
"Those commercial cyber thefts and hacking against government networks are crimes that must be punished in accordance with law and relevant international treaties," he said.