The abattoir in Ringsted, about 50 kilometres (30 miles) from Copenhagen, employs nearly 900 people and slaughters tens of thousands of pigs every week.
Danish Crown said 120 employees tested positive for the virus in a first round of tests of 600 employees present.
It then retested all the negative cases and detected 22 additional infections.
“For this reason, we are closing the abattoir for at least a week to try to break the chain of transmission among employees on site,” Danish Crown said in a statement.
All the employees must quarantine, said the company, one of Denmark's biggest exporters and the biggest pork product producer in Europe.
Several European slaughterhouses have been hit with the coronavirus in recent months, particularly in Germany.
The coronavirus cluster at Ringsted is the main active one in Denmark, where the number of cases has increased sharply in recent days.
On Friday, 169 confirmed cases of the coronavirus were recorded in Denmark, the highest figure for a single day since 25 April. This is according to figures sent by health authorities to the parliamentary parties, DR says. 79 of the new infected are in Aarhus, where the infection seems to have taken hold.
From Thursday to Friday, 145 people were found to be infected in Denmark and 68 in Aarhus.
Due to increasing infection rates in recent weeks, there are doubts about the next phase of the reopening of Denmark.
From a very low number of new infections at the beginning of the summer holidays, the number of infections has been steadily increasing since week 29.