The United Mine Workers of America have been notified of the planned lay-offs, The Canadian Press reported.
The decision comes in response to low coal prices and the company plans to resume operations once the prices recover.
A union spokesperson Gary Taje was quoted by the news agency as saying that the mine employs around 450 hourly and other workers.
Formal notices to the affected staff will be issued in the coming weeks.
Operations at the underground part of the mine will continue as usual.
Grande Cache Coal holds leases covering over 22,000 hectares in the Smoky River coalfield.
