Emission characteristics of laser induced plasma of soil in ambient gas are analyzed. The pulsed 1064 nm Nd:YAG laser is used as ablation source, a microscope plasma is generated in Ar and air atmosphere, and the emission spectral is recorded. The time evolution of the characteristic spectral lines and background are recorded and analyzed. By measuring the intensities of the characteristic spectral lines with Cr of different concentrations, the calibration lines are obtained in air and Ar atmosphere. The experimental results show that the Ar atmosphere has a marked enhancement effect on the emission characteristics of the laser induced soil plasma, increases the residence time, improves the linear relation between the species concentration and emission spectral intensity, and results in a better LIBS measurement sensitivity.