Only residents, police officers and those with business involving the G8 summit, held between June 6 and June 8, will be allowed through the two checkpoints in the fence.
Police have ordered a ban on demonstrations within 200 metres outside the fence from Wednesday through to the end of the summit.
A planned extension of that zone to a depth of several kilometres was struck down last week by a ruling in a regional court.
About 100,000 demonstrators are expected to gather in the area near the summit venue.
Rights activists from a number of "global justice" movements have complained that the security measures imposed are excessive.
Earlier in May, German authorities conducted raid on about 40 properties and targeted a number of groups and individuals said to be oraganising protests for the coming summit.
Police also targeted the so36.net, a German internet server that hosts a number of websites run by the groups targeted in the raids.
The UK media network, Indymedia UK, quoted Hanne Jobst of the Berlin Bethanien office as saying, "So far, the police only tried to split the resistance in the public media through hallucinating about an army of 'anarchists'. Now they will try to sabotage the organisational structures."
He said: "All attempts to criminalise this movement will not prevent us from exposing worldwide inequalities during the G8 summit."
The German government says the security measures are intended to avoid violent protest.
Previous G-8 summits have seen violent protest, notably in Genoa, Italy, in 2001 where one protester was killed.