Laser-induced fluorescence excitation spectrum of S0→S1 transition of 1-methylnaphthalene was obtained in supersonic jet condition. Theoretical calculations were conducted to study the geometry and energy of 1-methylnaphthalene at the ground and first excited state. Geometry optimization for the ground state was performed by DFT/B3LYP methods using 6-311++G(d,p) basis set. CIS/6-311++G(d,p) method was used to study the excited state. The excitation spectrum of 1-methylnaphthalene was assigned with the help of calculated vibrational frequencies and vertical excitation energies predicted by TDDFT method. It was found that the oscillator strength of the S0→S1 transition was enhanced by substituting a hydrogen atom of naphthalene with the methyl group although the Herzberg-Teller vibronic coupling effect still existed.