As a result of the deal, which includes a supply agreement, LM will expand its Jiangyin factory by 50% to accommodate the increased demand.
The blade is designed to withstand wind class II and III areas found off northern China's coast.
The first 4.5MW turbine is expected to be installed by Envision in H1 2018, LM Wind Power said.
Envision offshore business lead, Dick Xie said the new 4.5MW turbine will help contribute to reducing the levelised cost of energy.
According to Envision's brochure, the turbine will have a 148-metre rotor and a hub height of rougly 95-metres.
LM Wind Power offshore vice president, Alexis Crama, added: "The Chinese offshore wind market is expected to grow on average by 40% annually for the next five years.
"We look forward to further accelerating the development of a domestic offshore industry, helping China meet its growing demands for clean, renewable and affordable energy."
LM has supplied blades to Envision's onshore turbines in the past.
Yesterday (18 October) at China Wind Power, LM announced a deal with Goldwind to supply a 75.1-metre blade for its 6.8MW offshore wind turbine for wind class I sites.