The charity is considering reducing hourly pay rates for some of its care workers and making head office staff redundant as part of a plan to save £3m a year.
Its local authority funding, which amounts to about £20m a year and represents 75 per cent of its income, has been cut by 20 per cent.
The demonstration will take place at a centre run by Norwood in Crowthorne, Berkshire, this afternoon.
A spokesman for the trade union Unite, which is organising the protest, said staff had not been called away from the workplace to take part.
One employee of the charity, who asked not to be named, said 84 posts were at risk of redundancy.
He said Norwood was putting in place a new system under which those 84 people, including deputy managers, would have to reapply for 42 new posts, each with a salary of £20,000 - about £5,000 a year lower than that currently earned by deputy managers.
If they were unsuccessful, they would either have to accept redundancy or take jobs as support staff, earning £15,000 a year, he said.
"I love working for this charity, but I can’t afford to stay here," he said.
Norma Brier, chief executive of Norwood, said in a statement that Norwood greatly valued its workforce, who were understandably concerned, and was consulting them.
"These proposals are a consequence of national economic events beyond our control, and the subsequent effects upon Norwood of cuts in local authority budgets.
"We deeply regret having to propose reductions in salaries. We have no choice but to bring our historically above average pay rates for frontline staff into line with those of other social care providers.
"Failure to do so would put at risk the future of Norwood and all the people who depend on us for support."