Studying the transmission of light in biological tissues requires more accurate scattering phase function. It is necessary to study the effect of nucleus on the phase function. In this study, the Mie phase function, asymmetric factor g and second order parameter γ of monodisperse nucleated cells are modified based on the geometric scattering approximation theory, the effects of the morphological and optical parameters on the angular distribution of the Mie phase function and number of Airy peaks are analyzed. The variations of g and γ with wavelength, cell size, nucleus ratio and refractive index are numerically simulated. The results show that the distribution of the Mie phase function, number of Airy peaks, g and γ are not only related to the cell size, but also to the nucleus proportion and refractive index. The effect of intracellular optical structure cannot be ignored. Compared with HG phase function, the Mie phase function can describe the side-backscattering characteristics and calculate g and γ more accurately. The Mie phase function provides further theoretical support for studying label free cell detection methods and transmission characteristics of laser in biological tissues.