China is Cambodia's biggest aid donor, and its backing has bolstered Hun Sen in the face of criticism over what his opponents have said amounts to his destruction of democracy ahead of an election this year.
The deals, with their values not disclosed, were signed after talks between Premier Li Keqiang and his Cambodian counterpart Hun Sen.
They included one between the Overseas Cambodia Investment Corp and China Development Bank for a loan for a new airport in Siem Reap province, and another deal to build a highway from Phnom Penh to the beach resort of Sihanoukville - already a hub of Chinese investment. Cambodia's Royal Group of Companies and China Great Wall Industry Corp agreed to launch the southeast Asian nation's first communications satellite. Other deals included loans for electricity supply and support for agriculture.
Li and Hun Sen also discussed how to encourage Chinese tourists to visit Cambodia, and exports of sugar to China, said Eang Sophalleth, an aide to Hun Sen.
Li told Hun Sen China had another aid pledge of more than 1.2 billion yuan (HK$1.44 billion) for other projects.
Cambodia's Foreign Ministry said bilateral trade would reach US$6 billion (HK$46.8 billion) by 2020.