Gas temperature and density of Ar metastable state in DBD Ar (Ar/N2) plasma were measured using the tunable diode-laser absorption spectroscopy technology at low pressure. The variation trend of the densities of Ar metastable state 1s5, 1s3 and gas temperature with voltage, pressure, gas flow, electrode distance and N2 concentration was studied. The density of Ar metastable was obtained by calculating the absorption peak area of absorption line based on the Lambert-Beer law, while gas temperature was determined with Doppler width of the absorption line in Voigt fitting. We deduced that the main source of the Ar metastable was the electron-impact excitation from the ground state, and the main loss process was the electron quenching. In addition, the actual discharge power, the electron state and the collision between particles were responsible for the variation of gas temperature. It was found that, when the voltage and gas flow increasing, both temperature and densities of 1s5, 1s3 shown the similar trends, which increasing rapidly at first and then slowly. In addition, the variation with gas flow was smaller than that with gas flow. With pressure increasing, temperature and densities of 1s5, 1s3 increased till to a max value and then decreased. Meanwhile, the experimental data indicated that the pressure had a greater effect on spectral line width. To increase the electrode distance properly, the density of 1s5, 1s3 decreased while the gas temperature increased. N2 added to Ar presented a great negative effect on the density of Ar metastable state. Even 05% N2 added to Ar, the densities of 1s5 and 1s3 decreasedrapidly about to 50%, but then more N2 added, there was no obvious decrease about density.