Low pressure DC flowing discharge is used to study the formation of XeI  excimer in mixture of Xe/I 2. Fluorescence emission at spectral regions of 240～270 nm is examined. The characteristics of the emission spectra of the excimer and 253 nm intensity formed from mixture for different total gas pressures are reported. The investigation shows that 253 nm fluorescence intensity is the largest at 333 Pa and the correlated electron temperature of discharge plasma is 13.2 eV. The major reaction channel is Xe being excited to  3P by impact of high speed electron, and then XeI(A,B,C) being formed by collision between Xe( 3P) and I 2.