The 21-year-old is accused of conducting research and buying a knife and other items to help him carry out an attack, police said in a statement.
The suspect from Birmingham, central England, was arrested in the city on March 29.
He was additionally charged over allegedly having copies of the "Anarchist Cookbook 2000" and "Mujahideen Poisons handbook", which police said would be useful to a person preparing an act of terrorism.
A 23-year-old woman was also charged, accused of sending beheading videos and propaganda by the Islamic State group to others encouraging acts of terror.
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Four people were killed and dozens injured in the attack by 52-year-old Khalid Masood, who had been living in Birmingham before the central London attack.
Britain kept its terrorism threat level at "severe" following the Westminster assault.
The Birmingham terror charges come a day after a man suspected of preparing acts of terrorism was arrested in London, as he was trying to leave Britain from a train station served by Eurostar.