Variation of graphene Raman G peak splitting due to uniaxial strain and absorption of polyaromatic moleculars on both sides are studied by fifth-nearest neighbor force-constant model. The calculation results show that symmetry lowering is responsible for the G peak splitting, where G peak splits into G+ and G- peaks by lifting the energy degeneracy of in-plane longitudinal and transverse optical phonons at Γ point. Under uniaxial strain, the elongation of C—C bonds reduces the force-constant and softens the in-plane optical phonons which induce red shifts of both G+ and G- peaks. The different strains produced by polyaromatic molecules along its long and short edges lead to red shift and blue shift of the two in-plane optical phonons relevant to G- and G+ peaks, which gives a plausible explanation to the different G peak splitting of the recent Raman experiment on graphene with uniaxial strain and graphene sandwiched by the polyaromatic molecules.