Alstom, which makes French high-speed TGV trains, filed the complaint in London, where Eurostar is based, to attempt to force the suspension of a €600 million ($835 million) deal for 10 high-speed trains.
But judge Geoffrey Vos said in his ruling at the High Court in London, "I dismiss Alstom's application."
The judge said Alstom did not have a "serious case" and that granting a suspension "would be against the public interest."
Eurostar, which is 55 percent-owned by the French national rail operator, and Siemens had united to strongly contest Alstom's legal bid. The deal to buy the ICE trains built by Siemens sparked a row between Germany and France.
The French government criticised the deal and argued that the German train did not meet safety standards in the Channel Tunnel, which links France to Britain. A defiant Alstom said Friday it would pursue its legal challenge.
The row over Eurostar's new train order is part of a Franco-German race for dominance of Europe's high-speed rail links.
German train operator Deutsche Bahn wants to be able to run its own services through the Channel Tunnel to Britain with the aim of linking Frankfurt to London in a journey lasting less than five hours.
This month Deutsche Bahn tested one of its Siemens trains in the Channel Tunnel, making it the first non-Eurostar train to use the link. The European Union has backed moves to open up the tunnel to competition.