The plan will span nine projects that total 1,100 km (683 miles) in length, the country's powerful economic planner, the National Development and Reform Commission, said in an online statement on Monday.
The projects will be built over the years to 2020, and are part of a wider plan that will stretch to 2030, it added.
The current population of the three areas is estimated at around 110 million, and by the time the plan is complete, the so-called Jing-Jin-Ji project will span 212,000 sq km (82,000 sq miles), or more than twice the size of South Korea.
The expanding railway networks have cut commute time in the region significantly, said Steven McCord, research head at real estate service firm Jones Lang LaSalle (JLL).
"It was not possible to go all the way from Beijing to Binghai and that's a one-hour trip now. It's now also possible to go between Tianjin and Tangshan in less than 30 minutes, which was previously several hours' drive," he said.