Abstract: Nonlinear laser spectroscopy has been widely applied for species trace in the gas-media. Forward DFWM with a self-stability beam-spiltting system was demonstrated in iodine vapor at different temperatures and pressures. It is found that the effects of the variable temperature and pressure on DFWM spectra structure (555-556 nm and 558-559 nm) are vivid under the saturated pumping and probing situation, and first of all, a wavelength (555.1 nm) sensitive to temperature in the atmospheric pressure is found. Also the wavelengths(558.81 nm) insensitive to temperatures, which the wavelength can be used to measure the gas-phase media concentration at varied temperatures. Effects of different temperatures and atmospheric pressures on the DFWM spectroscopy in iodine vapor at atmospheric pressure are of importance to trace atom, molecular and radical in combustion diagnosis.