Defence Minister Lourenco was recently named to succeed President Jose Eduardodos Santos, who has ruled Angola for 37 years, as head of the MPLA party.
Dos Santos will step back from frontline politics following the transition and is set to become the party's honorary chief.
"We cannot accept impunity in the face of corruption," Lourenco said Monday as he opened a student event in the country's northeast.
He condemned "bribes which have to be paid by entrepreneurs wanting to invest in the country".
Lourenco had earlier railed against "the great sickness" of corruption during a visit to Huila state in the country's southwest on Saturday.
He has also promised improvements to Angola's ailing agricultural sector and health infrastructure.
As the incoming leader of the MPLA, Lourenco will become president of the oil-rich country in August elections if the party wins the vote as expected.
Dos Santos has often been criticised for protecting a corrupt elite and handing his family key roles in state firms.
His daughter Isabelle, who is considered the richest woman in Africa, was last year made the head of the national oil company.
The main opposition party called Lourenco's crusade against graft a facade.
"There won't be any change while the MPLA are in charge. The current president will continue to steer from the backseat even if he has employed a new driver," the Unita party said in a statement.
Angola is ranked 164 out of 176 countries for its level of corruption by graft watchdog Transparency International.