Terrorist Khalid Masood ploughed a 4X4 into crowds on the bridge before crashing into the gates of the Palace of Westminster and stabbing PC Keith Palmer to death at 2.40pm last Wednesday.
Masood was shot by police.
In a show of defiance and solidarity, officers from across London will join hands and walk the length of the bridge in a bid to show terrorists “they will not achieve anything” by attacking the capital.
As many as 3,000 officers are expected to join the march, organised by Westminster Police.
Ken Marsh, chairman of the Metropolitan Police Federation, told the Standard: “This is a show of solidarity.
“We want to show terrorists that they can attack us and they can attack our city but they won’t achieve anything.
“People will pull together.”
The march, held at the exact time PC Palmer was fatally knifed, is planned to coincide with a similar tribute which will see around 500 faith leaders from across the country flock to the scene of the worst attack on the capital since 7/7.
Paying tribute to Pc Palmer, colleague Pc James Aitkenhead, said in a statement: "Keith was a genuinely nice person; nobody had a bad word to say about him.
“When I heard what had happened I knew it would be him because that's just the sort of guy he was, to step straight in when others might step back.
"We will miss him so much."
Spanish teacher Aysha Farde, 43, was also killed in the attack after being hit by Masood’s car.
The mother-of-two had been crossing the bridge to pick her two daughters, aged eight and 11, up from school.
Mrs Frade, described by friends as “beautiful and lovely”, grew up in Notting Hill and worked DLD London College.
Kurt Cochran, 54, also died after being hit by the car.
The American national had been visiting London as part of his 25th wedding anniversary celebrations with wife Melissa.
In a touching statement, Mr Cochran’s family described him as an “amazing individual”.
They said: “He was an amazing individual who loved everyone and tried to make the world a better place.
"He left a legacy of generosity and service that continues to inspire us.
“We are deeply saddened to lose him but are grateful that the world is coming to know him and be inspired by him.”
“Kind and gentle” window cleaner Leslie Rhodes, 75, was the fourth victim of the attack.
Mr Rhodes, from south London, formerly cleaned Winston Churchill’s windows during a career spanning 50 years.
Client and friend Janine Roebuck told MailOnline: “Les was my much loved window cleaner for 20 years.
“You couldn't wish to meet a kinder, gentler man. He cleaned the windows of Chartwell - Winston Churchill's home - for many years.
“It was something he was so proud of.”
Officers will gather from 2.15pm on Wednesday to walk from the south to the north side of the bridge.
A minute's silence will be held in memory of the victims at 2.40pm.
A statement posted on the Met Police Federation’s website reads: “An event is planned on Westminster Bridge to mark a week since the terrorist attack in which our colleague PC Keith Palmer died.
“The intention is to link hands across Westminster Bridge from the south to the north at the exact moment the attack began.
“The organisers say the event will show "we will not be divided. Linking all nations, faiths, orientation and sexes."
“They are asking for as many Met colleagues who attended the scene that day to come to pay their respects, as well as victims, witnesses and anyone else.”
The tribute comes just days after a group of women joined hands along the bridge on Sunday.
Westminster Bridge will be closed to traffic during the event.