The heritage railway launched its £1.5 million "survival fund" back in April after bosses voiced fears it may not survive its current financial woes.
It has blamed falling passenger numbers after the pandemic and escalating costs for its financial predicament.
In an update, a spokesperson for SVR said the fund had now reached £320,000.
The increase in the survival fund follows a "record-breaking" Spring Diesel Festival in May that saw its highest ever visitor attendance.
It also comes ahead of SVR's annual 'Step Back to the 1940s' weekends.
The annual events, which see volunteers and visitors dress up in wartime costume, is one of the most popular put on by SVR.
This year the 40s weekends take place on June 24 and 25, and July 1 and 2.
Tickets and information are available at svr.co.uk