In this study, a series of carbon nitride nano-homojunction (CNHM) decorated carbon nitride (g-C3N4) nanocomposites (g-C3N4/CNHM) was synthesized by the facile solvothermal method to maximize the photocatalytic and nonlinear optical performances. The structure, optical and electrical properties of the g-C3N4/CNHM nanocomposites were investigated by various characterization techniques, including Fourier-transform infrared, X-ray photoelectron spectroscopy, X-ray diffraction patterns, Scanning electron microscopy, UV-Vis diffuse reflection spectra and Brunauer-Emmett-Teller method. The photocatalysis and nonlinear optical performance of the g-C3N4/CNHM nanocomposites are shown to be dependent on the CNHM loadings. The highest photocatalytic activity and obvious nonlinear optical performance were observed for g-C3N4/CNHM-2%. A rational mechanism for degrading pollutants and observed nonlinear property was proposed, which could be ascribed to the efficient interfacial charge transfer between g-C3N4 and CNHM. The efficient charge separation efficiency was confirmed by the photoluminescence spectroscopy, electrochemical impedance spectroscopy, and photocurrent spectroscopy studies. These results indicate that the multifunctional hybrid materials with tunable optoelectronic performances can be obtained by adjusting the content of CNHM in g-C3N4/CNHM nanocomposites.