The military cuts President Xi Jinping announced on Thursday will mainly target "troops equipped with outdated armaments, administrative staff and noncombatant personnel", Ministry of National Defense spokesman Yang Yujun said at a news conference in Beijing.
The decision to cut 300,000 troops will be the country's fourth such major reduction since the 1980s.
The reduction will be completed by the end of 2017 in order to optimize the structure of Chinese forces, Yang said.
Since the 1980s, China has reduced the size of its military in three stages-by 1 million, 500,000 and 200,000 personnel. There are currently 2.3 million members.
Xi's announcement "fully demonstrates China's sincerity and hope in jointly championing peace, seeking development and enjoying prosperity with various countries in the world", Yang said.
The decision also shows the country's "proactive, responsible attitude toward advancing international arms control and disarmament", the spokesman added.
Asked if the announcement signifies the start of a new round of national defense and military reform, Yang said China "will come up with some new reform measures and proactively and steadily press ahead with reform of national defense and the military".
Some countries and recent media reports have again raised questions over the size of the People's Liberation Army, the world's largest.
Yang said that comments made about China's alleged threat "run counter to the facts and are irresponsible".
The country is still undertaking demanding tasks in championing national unification, securing state sovereignty and ensuring its development and interests, he said.
The PLA undertakes noncombatant actions and missions such as disaster relief, international peacekeeping, and search and rescue work. China is also faced with threats posed by regional terrorism, separatism and extremism, he added.
"Therefore, our military needs to maintain a certain scale, which is totally for defense purposes," he said, adding that China never sought, nor seeks, hegemony and expansion.
Yang also said the defense budget needs to maintain a certain scale, as the overall level of China's arms and equipment "is comparatively lagging behind".
Timeline
Troop reductions since the 1980s
1985: China decides to cut 1 million troops from the People's Liberation Army to focus on accelerating economic development and strengthening soldiers' quality.
1987: PLA troops reduced to 3.23 million from 4.23 million.
By 1990: PLA troops lowered to 3.19 million.
1997: PLA troops to be cut by 500,000 to 2.5 million within three years.
2003 to 2005: Further reduction of 200,000 to 2.3 million, with the army accounting for the lowest proportion in the country's history.