The UN says it is investigating eight new reports of sex abuse, following more than 20 previous allegations.
One 14 year-old says she was raped by an armed soldier near the airport.
The 120 soldiers who will be repatriated are from Congo-Brazzaville. During the investigation, they will be confined to barracks.
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Last week the UN said European troops were implicated in child sex abuse allegations.
Parfait Onanga-Anyanga, the UN envoy for CAR, travelled to Bambari, the country's second biggest city where the latest abuse allegedly occurred, on Thursday.
He expressed outrage and shame.
There is "sufficient initial evidence" that five of the alleged victims are minors and one adult has been sexually exploited, according to a fact-finding expert sent to the city.
The NGO Human Rights Watch said most of the abuse occurred while the Congolese peacekeepers were temporarily deployed to protect the city's airport.
UN assistant secretary-general Anthony Banbury said there are likely to be 22 confirmed allegations of sexual abuse or exploitation in the UN's peacekeeping mission in CAR. That may rise as a result of the latest allegations.
Last week, the UN said a number of girls aged between 14 and 16 alleged they had been raped by Georgian members of the EU's operation Eufor in CAR.
A seven-year-old girl and a nine-year-old boy said they were abused by French troops.
The troops were sent to stem violence between Christian militias and largely Muslim rebels.
The rebels seized power in March 2013 - in response, the militias took up arms against them.
Last December an independent panel criticised the UN's handling of abuse allegations in the CAR, calling it "seriously flawed" and a "gross institutional failure".
It accused senior UN officials of abusing their authority by failing to take action over allegations of abuse by soldiers from France, Equatorial Guinea and Chad.
A 10,000-strong UN force took over a peacekeeping mission in September 2014.
More than 100 UN peacekeepers will be sent home from the Central African Republic after an investigation into sex abuse allegations, the UN says.