Exploiting highly efficient noble metal-free co-catalysts with promoted photocatalytic performance of the photocatalysts is of great importance. Herein, binary LaCoO3/g-C3N4 hybrids consisting of LaCoO3 co-catalysts in-situ growth on the surface of g-C3N4 nanosheets were constructed via a facile mixed-calcination process and utilized for the photocatalytic degradation of methyl orange (MO) in aqueous solution at room temperature under visible light irradiation (lambda > 420 nm). As expected, all the LaCoO3/g-C3N4 hybrids illustrated dramatically ameliorated photocatalytic efficiencies compared to the pristine g-C3N4. More importantly, the optimal photodegradation rate constant of LaCoO3(3.0 wt%)/g-C3N4 reached about 0.00346 min(-1), which was almost 3.2 times higher than that of pure g-C3N4 for MO degradation, which could be originate from the function of LaCoO3 co-catalysts acted as excellent electron collectors for capturing the electrons generated by g-C3N4, effectively suppressed the photogenerated charge carriers recombination and prolonged the lifetime of the separated electron-hole pairs. Additionally, radical trapping experiments confirmed that the photogenerated holes and superoxide radicals were responsible for the MO decomposition. Ultimately, a plausible photodegradation mechanism was also proposed. This work could bring new opportunity for the rational construction of highly efficient noble metal-free co-catalysts with enhanced photocatalytic efficiency of g-C3N4 for applying in environmental remediation and energy conversion.