In the present paper, a dielectric barrier discharge(DBD) plasma was generated at low pressure in a DBD device with the eletrode distance of 10cm and using Ar as working gas. The changes in electronic temperature and density in the discharge cavum were studied by means of emission spectrometry. The changes in electronic temperature measured by using corona model were obtained. The variations in electronic density were analyzed using 750.4 nm line intensity. It was found that the plasma electronic temperature and density is various at different positions in the discharge cavum. With the measuring point moving from cathode to anode, the electronic temperature firstly increases slowly, then decreases quickly. While the electronic density increases slowly at first, and then rapidly.