In its two-year progress report, the Public Contracts Scotland (PCS) portal - which was set up by the Scottish Procurement Directorate - said the number of new firms registering for the service had risen from 17,447 to 24,752.
The total has now reached more than 49,000 and PCS expects 50,000 businesses to be signed up by 31 March.
Public sector bodies signed up to the site can post details of contracts, which companies can then bid to fulfil.
About 9 billion-worth of work is awarded through the website each year.
Finance secretary John Swinney said: "By opening up contract opportunities to business and encouraging competition, there have been significant cost-savings to the public sector."
PCS said 84 per cent of the companies registered with the portal were classed as small businesses, with 250 or fewer staff.
A spokesman for the Federation of Small Businesses in Scotland said the PCS website was a great help to small companies, but warned that more could be done to reduce the form-filling and other pieces of bureaucracy involved in procurement.
He added that all public bodies must be encouraged to use the site rather than setting up their own online procurement systems, otherwise it would defeat the point of having one centralised portal.