Measurements of the electron density in a 5 kW CW transverse-flow CO2 laser gag discharge are presented. Experiments were performed with a single Langmulr probe. Electron density was evaluated using P. E. Smys' thick shealth expression for a flowing plasma. The spatial distribution of electron density and an analysis using the electron continue equation are given. In the condition of pressure 42 Torr, discharge current 20 A, the electron density is about 3×1011cm-3 and along the flow, the distribution was unhomogeneous, the maximum value occured at 3 cm from the top edge of the anode in the floe direction. The explaination of the experimental results is given by the continuity formulation of electrons, the theory coincides with the experiment.