The poll predicts a voting turnout of 71.6 percent for the election.
A coalition of pro-independence parties, comprising the Republican Left of Catalonia and the Democratic Convergence of Catalonia (CDC), has pledged to secure the region's secession from Spain should it win the vote in September.
Over 80 percent of Catalans who participated in the November 2014 informal referendum on independence supported secession from Spain. Over two million people out of the estimated 5.4 million eligible voters participated in the ballot.
Spanish Prime Minister Mariano Rajoy has repeatedly rejected Catalonia's right to secede.