0435 GMT September 19, 2019
The focus of the spending is on building a China-Pakistan Economic Corridor (CPEC) — a network of roads, railroads and pipelines between the two.
They will run some 3,000 km (1,865 miles) from Gwadar in Pakistan to China's western Xinjiang region, BBC reported.
The projects will give China direct access to the Indian Ocean and beyond.
This marks a major advance in China's plans to boost its economic influence in Central and South Asia, correspondents say, and far exceeds US spending in Pakistan.
"Pakistan, for China, is now of pivotal importance. This has to succeed and be seen to succeed," Reuters quoted Mushahid Hussain Sayed, chairman of the Pakistani Parliament's Defense Committee, as saying.
Pakistan, for its part, hopes the investment will boost its struggling economy and help end chronic power shortages.
Leaders are also expected to discuss cooperation on security.
Xi will spend two days holding talks with his counterpart Mamnoon Hussain, Prime Minister Nawaz Sharif and other ministers.
Deals worth some $28 billion are ready to be signed during the visit, with the rest to follow.
Under the CPEC plan, China's government and banks will lend to Chinese companies, so they can invest in projects as commercial ventures.
Some $15.5 billion worth of coal, wind, solar and hydro energy projects will come online by 2017 and add 10,400 megawatts of energy to Pakistan's national grid, according to officials.
A $44 million optical fiber cable between the two countries is also due to be built.
Pakistan, meanwhile, hopes the investment will enable it to transform itself into a regional economic hub.
Ahsan Iqbal, the Pakistani minister overseeing the plan, told AFP that these were "very substantial and tangible projects that will have a significant transformative effect on Pakistan's economy".