China could boost its liquefied natural gas import capacity by nearly fourfold within two decades as it seeks to use more of the cleaner-burning fuel.

A Ministry of Transport proposal calls for a total of 34 coastal terminals with a combined annual import capacity of 247 million tons by 2035, said people with knowledge of the draft plan. That compares with capacity of 67.5 million tons at the end of last year, according to BloombergNEF. The plan is preliminary and...