The platform, "From the Desk of Donald J. Trump" appears on www.DonaldJTrump.com/desk.
Mr. Trump was suspended by Twitter and suspended by Facebook and YouTube after the Capitol riots in January.
The former president has since been publishing statements by press release - which the new website will now host.
Users will be able to like posts - and also share them on Twitter and Facebook accounts.
The move comes a day before a choice is due from Facebook's Oversight Board on whether to permanently suspend Mr. Trump.
Mr. Trump's senior adviser, Jason Miller, had previously said a new social media platform was to be propelled. "This new platform is going to be big," he said in March.
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But Mr. Miller tweeted on Tuesday that the new website was not the social media platform he had previously advocated.
"We'll have additional information coming on that front in the very near future," he said.
"President Trump’s website is a great resource to find his latest statements and highlights from his first term in office, but this is not a new social media platform," senior advisor Jason Miller told Fox News.
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The website is reportedly developed by Campaign Nucleus, the digital services company founded by Mr. Trump's former campaign manager Brad Parscale.
"In a time of silence and lies," a video Trump posted to the platform Tuesday night says. The video then plays news reports describing his suspension from Twitter.
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"A beacon of freedom arises. A place to speak freely and safely," the video continues, showing the new platform. "Straight from the desk of Donald J. Trump."
The technology appears to be powered by Campaign Nucleus— the "digital ecosystem made for efficiently managing political campaigns and organizations".
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Several posts on the site repeatedly claim that last year's presidential election was stolen.
Facebook's Oversight Board will announce its decision on whether Mr. Trump is to be permanently banned from the platform on 09:00 EST (14:00 BST).
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If he is permitted back on to the site, Facebook will have seven days to reactivate his account.
YouTube has said they will reactivate Mr. Trump's account when the menace of "real-world violence" diminishes.
Twitter, where Mr. Trump had 88 million followers, has outlawed him permanently.
A Twitter spokesperson told the BBC: "Generally, sharing content from the website referenced is permitted as long as the material does not otherwise violate the Twitter Rules".
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