Before holding talks with King Salman, he said he hoped to lift "co-operation in various fields to a new level".
Later this week, Mr Xi will travel to Saudi Arabia’s regional rival, Iran.
China buys large amounts of oil from both states, and says it does not want to take sides in a bitter dispute over Riyadh’s execution of a Shia cleric.
Saudi Arabia recalled its ambassador from Iran earlier this month in protest at the storming of its embassy in Tehran by a crowd angered by the killing of Sheikh Nimr al-Nimr.
"Regarding some of the region’s problems, China has always taken a balanced and just position," Vice-Foreign Minister Zhang Ming told reporters on Monday when asked whether the president would attempt to mediate in the dispute.
‘Mutual trust’
Mr Xi was greeted at Riyadh’s airport on Tuesday by Saudi Arabia’s Deputy Crown Prince and Defence Minister, Mohammed bin Salman.
"Since China and Saudi Arabia forged diplomatic ties 26 years ago, our relationship has developed by leaps and bounds, with mutual political trust deepening continuously and rich results in co-operation in various fields," Mr Xi was quoted as saying by China’s official Xinhua news agency.
"I believe that my visit will be a friendly trip with fruitful achievements, thus conducive to lifting our co-operation in various fields to a new level and to elevating the collective co-operation between China and [Gulf Co-operation Council] nations," he added.
Xinhua reported that Saudi Arabia was China’s biggest supplier of crude oil, and bilateral trade reached $69.1bn (£48.7bn) in 2014.
On Wednesday, Mr Xi and King Salman will inaugurate an energy research centre in Riyadh and open remotely the Yasref oil refinery, a joint venture between Saudi Aramco and China’s Sinopec.
The official Saudi Press Agency reported that the two companies signed a framework agreement for strategic co-operation on Tuesday, and also that the Saudi and Chinese governments had signed a memorandum of understanding to build a high-energy nuclear reactor.
After his visit to Saudi Arabia, Mr Xi will travel to Egypt, where he will meet President Abdul Fattah al-Sisi and deliver a speech to the Arab League on China’s policies in the Middle East, and then Iran.
Mr Xi will arrive in Tehran only days after crippling economic sanctions against Iran were lifted as part of a long-term nuclear deal with world powers, including China.
