It has been reported that beta-MnO2 has photocatalytic activity for the oxidative-coupling of 2-naphthols into 1,1 '-bi-2-naphthols. Nevertheless, it is hard to exclude the possibility that the oxidative-coupling of 2-naphthols is initiated by beta-MnO2 catalysis in dark due to the insufficient investigations in the related reports. In the present work, the oxidative-coupling of 2-naphthols into 1,1 '-bi-2-naphthols with different phases MnO2 catalysis in dark and under visible-light irradiation were systematically investigated. The results revealed that the oxidative-coupling of 2-naphthols is jointly initiated by MnO2 catalysis and O-2-oxidation, not by MnO2 photocatalysis. Among the alpha-MnO2, beta-MnO2, gamma-MnO2 and delta-MnO2 catalysis, beta-MnO(2)catalysis has the optimal performance, its selectivity for the oxidative-coupling of 2-naphthols into 1,1 '-bi-2-naphthols is close to 100%, and its catalytic capacity could be well retained after multiple using. Our findings provide comprehensive and accurate understanding the catalytic role of MnO2 for the oxidative-coupling of 2-naphthols into 1,1 '-bi-2-naphthols. [GRAPHICS] .