Abstract: This research study about gas flow characteristics to a nozzle with assistance hydraulic analogies method. Characters gas flow vary depending upon character of static pressure, nozzle geometry and flow rate. Gas flow is very tough to identify because not seen directly by eye. So, it requires a special method to observe gas flow form. The proper way to examine it namely analogized gas medium with water. Research carried out by using the three forms nozzle, namely; convergent, convergent-divergent and parallel nozzles. Structures and shock-wave of jet observed using topography visualization method. The aim of research is appraise characteristics of jet, determine the profile of static pressure velocity and variations around locations of jet, understand existence the flow structure and shock-waves and predict the noise intensity from gas flow. Research shows that characteristics and structure of jet on the water flow is synonymous to gas flow. Flow rates and variation in profile of static pressure around jet at the critical ratio, Rh =1.5 is relative different to three nozzles that were tested. The jet structure is obviously different the critical ratio, Rh = 1.5 and ratio of Rh>1.6 were relatively equal. This study obtained that hydraulic analogy was able to give exact comprehension about the jet structure, obviously the shock-wave and understand of gas flow mechanisms. This study recommends that a new study on the characteristics nozzle and structures is hoped to give detailed information and description of flow characteristics and jet structures.