A series of Mn-1.56(Co1-xAlx)(0.96)Ni0.48O4 (x=0.1, 0.2, 0.3, and 0.4) films were prepared by the chemical solution deposition method and then post-heated at 150 degrees C for 300h. Scanning electron microscopy and x-ray diffraction revealed remarkable improvements in relative density and crystallinity in post-heated Mn-1.56(Co1-xAlx)(0.96)Ni0.48O4 (x=0.1, 0.2, 0.3, and 0.4) films. From x-ray photoelectron and Raman spectroscopy, it was found that the Mn3+/Mn4+ ratio decreases after post-heating, which leads to a decrease in Raman mode intensity. Furthermore, spectroscopic ellipsometry results show that both the refractive indexes and extinction coefficients of post-heated films are higher than those of annealed films in the visible range. However, the band gaps of all the films decreased significantly after the heating process. These investigations suggest that the post-heating treatment may be preferable for fabricating Mn1.56Co0.96Ni0.48O4 thin films for optical detection.