Lu was born on 2 December 1930 in British Hong Kong, into a middle-class family that hailed from Hua County (now Huadu), Guangdong province. When the Japanese attacked Hong Kong in 1941, his father sent him to Hua County for safety, where he became familiarized with agricultural practices. He returned to Hong Kong two years later for middle school. This experience with Japanese invasion made him sympathetic to the Communist cause, and in 1947 he joined the New Democratic Youth Association of Hong Kong, which was secretly led by the Communist Party of China, and the Party itself in August 1949.