Effect of volume strain (-11%~11%) on the structure, stability, electronic structure and optical properties of cubic paraelectric phase PbTiO3 was calculated and analyzed via first-principles method. It is found that formation enthalpy increases and stability decreases for PbTiO3 after volume strain. And the influence of compressive strain on the stability of PbTiO3 is greater than that of tensile strain. When subjected to tensile strain, cubic PbTiO3 changes from direct bandgap semiconductor to indirect bandgap semiconductor, and bandgap increase first and then decrease with the increase of strain. When compressive strain occurs, from the analysis of complex dielectric function, complex refractive index and absorption coefficient, the light absorption capacity of PbTiO3 weakens under natural light, with fluctuations in individual wavelength. When tensile strain occurs, dielectric peak and absorption peak redshifts, and light absorption capacity of PbTiO3 in visible light range is enhanced. Furthermore, when strain increases to 11%, the aforementioned absorption capacity outclasses than that in intrinsic cubic phase.