A novel tilted long-period fiber grating (TLPFG) written by high-frequency CO2 laser pulses was experimentally demonstrated. The coupled-mode theory was modified in order to theoretically analyze the TLPFG. The effects of tilted refractive index modulation on the spectral properties of the TLPFG were studied. The influence of tilted angle on the modes coupling of TLPFG was analyzed. Theoretical analysis is in accord with experimental results. The experimental results show that the TLPFG written by high-frequency CO2 laser pulses has many novel properties. The coupling coefficient of low-order cladding modes is higher than that of high-order ones, and tilted refractive index modulation not only can enhance the coupling coefficient between the core fundamental mode and cladding modes, but also can stimulate the coupling between core fundamental and high-order cladding modes. The written efficiency can be dramatically improved by increasing the tilt angle.