President Hu Jintao, Premier Wen Jiabao and other high-ranking Chinese officials greeted a large number of the country's delegation.
Four years after cleaning up with 51 gold medals in Beijing, China slipped to second with 38 gold, 27 silver and 23 bronze medals, ranking behind the United States, who won 46 gold medals.
However, it was China's best finish at an overseas Olympics.
"The Games was another demonstration of China's national image and the country's achievements in sports development and reform," Liu said.
"The Chinese delegation accomplished its best result at an overseas Olympics, which is quite inspiring and encouraging," he said. "Chinese athletes also enhanced their friendship and communication with athletes from other countries during the Games."
More than 390 Chinese athletes took part in 23 events in London and broke six world records and six Olympic marks.
Chinese athletes continued to thrive in the country's traditionally strong events such as diving, table tennis, badminton and shooting by overcoming team reshuffles, injuries and rule modifications. They also made breakthroughs in some surprising events, including sailing, fencing and boxing, Liu said at the conference.
China had its best performances yet in athletics and swimming, which award 81 gold medals out of the 302 in total.
"China only took one gold in athletics and swimming at the Beijing Olympics, and the competitiveness of our athletes in these events was tremendously improved during preparations for the London Games," Liu said. "Athletics and swimming contributed six gold, two silver and eight bronze in London, helping the delegation to accomplish its targets and balance the country's medal-collecting ability in a wider range of events."
According to Liu, China claimed titles in eight sports for the first time, and 62 percent of the athletes, who were attending their first Olympic Games, contributed 23 gold medals.
Chinese sailor Xu Lijia, who won the country's first gold in the women's Laser Radial class and was appointed as flag bearer for the closing ceremony, said she hoped her achievement would help get more Chinese to understand and enjoy sailing.
"I had taken several World Cup titles this year and a runner-up finish in the World Championships. I knew I was capable of winning Olympic gold," said the 24-year-old. "I am satisfied with my performance, and from the perspective of the event, the gold is a considerable boost and inspiration to the development of the sport. I hope sailing will become more readily available to families in China."
Xu, a college student learning business administration at Shanghai Jiao Tong University, said she will take a break from the sport and return to campus for two years before beginning preparations for the 2016 Rio de Janeiro Olympics.
Zou Shiming, who won his second Olympic title in light flyweight boxing in London, said he was happy his last Games ended on a winning note.
"This was my last Olympics, and I may retire after next year's National Games," said the 31-year-old. "I shouldered lots of pressure at the Beijing Games, because it was China's first boxing Olympic medal.
"I was quite relaxed before going to London, although a lot of boxers wanted to beat the defending champion," he said. "The victory is a fine ending to my career and also a special gift for my child. I hope he will be inspired by my tenacious spirit and become a brave and responsible person."