The comments by Gen. Zhang Qinsheng, deputy chief of the general staff of the People's Liberation Army, come amid longstanding Western claims that hackers inside China are behind a range of cyberattacks.
"China has always been embarking on peaceful development and the development of China is by no means a threat," Zhang told a conference on land warfare at the Royal United Services Institute, a defense think-tank in London.
"China does not pursue hegemony. We will not do it even when we grow stronger. This is not only the basic state policy, but also a solemn commitment to the people of the world."
In March, China announced that its defense budget would rise 12.7 percent in 2011 to 601.1 billion yuan ($91.7 billion), fuelling regional concerns about Beijing's military build-up in addition to its economic clout.
Addressing an audience of senior military officers from countries including the United States, Britain and Brazil, Zhang said China's armed forces needed "reform" to win increasingly high-tech conflicts.
"The (Chinese) army has to be modernized to fight modern wars in an informationalized age. This is a major challenge facing us," said Zhang, speaking through an interpreter.
He said China's aims had always been defensive, but added: "The goal of modernization of our army is to transform it from a regional defense force to an all-theatre maneuvering force."
Zhang's words come just days after Chinese state media reported that the military had set up an elite Internet security task force tasked with fending off cyber-attacks.
But the Global Times newspaper denied that the initiative, in which the military has reportedly invested millions of dollars, is intended to create a "hacker army", saying that China was relatively weak in cyber-security.
The United States, Australia, Germany and other Western nations have long alleged that hackers inside China are carrying out a wide-range of cyber-attacks on government and corporate computer systems worldwide.