Five memorandums of understanding (MOU) were signed following a meeting between Mr Xi and Mr Bainimarama.
They cover increased economic and defence cooperation, the "provision of goods to address climate change", and visa exemptions for Fijians travelling to China.
One of the MOUs includes the establishment of a Chinese cultural centre in Fiji.
Mr Xi is also hosting bilateral meetings with leaders from Samoa, Vanuatu, Niue, Tonga, Papua New Guinea and the Federated States of Micronesia, and a round-table discussion with all the Pacific leaders.
Pacific a diplomatic focus for China and India
His visit comes after Indian prime minister Narendra Modi stopped over in Fiji also to court regional leaders, who form one of the largest voting blocs at the United Nations.
Both leaders targeted the Pacific as a vital stop on their way home from the recent G20 summit in Australia.
During a traditional welcoming ceremony in the tourist town of Nadi last night, Mr Bainimarama said Fiji wanted China to be fully engaged in the Pacific.
In a thinly veiled swipe at Australia and New Zealand, he said China had been "a true friend of Fiji" and had never interfered in Fiji's internal politics.
Australia and New Zealand loudly criticised Mr Bainimarama and imposed sanctions on Fiji after he seized power in a military coup in 2006.
Mr Xi said that Fiji is the first Pacific island country to establish diplomatic relations with China and the two countries have witnessed ever-deepening political mutual trust and fruitful practical cooperation over the past 39 years.
"China views Fiji as a cordial friend and an important partner'" Mr Xi said.
"China supports the people of Fiji in choosing their own development path and improving livelihoods."
Before his arrival in Fiji, Mr Xi released a statement saying he would meet the leaders of all Pacific island countries that have diplomatic ties with China to draw what he called a blueprint for future mutually beneficial cooperation.
"The friendly exchanges between the people of China and Pacific Island countries date back to a long time ago," he said.
"We feel a natural kinship with each other."