An experimental and numerical investigation of the ejector-jets focusing on its geometric parameters that effect on thrust performance was carried out. The area ratio of the primary nozzle that was tested in the present study was 2.17 and 3.18, while the ratio of the length to the diameter of the duct downstream the primary nozzle inlet had values of 3.41, 6.82, and 10.23. Internal flow properties of ejector-jet were estimated by comparison experiment data and CFD analysis for basic study of ejector-jet thrust performance. For examination of thrust performance, the thrust ratios increased with increase in L/D. Especially at AR=2.17, the maximum thrust augmentation was 33 percent for the shortest L/D. It is expected that the increase of mixing duct length of ejector-jet will be helpful in a thrust performance by improving mixing efficiency.