Abstract: The segmented arc heater is an ideal thermal protection test equipment for having a wide range of enthalpy. In order to broaden the simulation range of pressure, the analysis method of the segmented arc heater internal flow is developed. The prediction results match the high pressure operation test results. To solve the problems in the high pressure test, some technical measures have been taken the pressure and heat resistance segments are developed cooling is strengthen and the electrode is shortened. The internal protective measures are studied to reduce surface oxidation and heat loss of segments. The operational mode is explored to solve the string arc problem in the high pressure operation test. The operation pressure of the test exceeds 10 MPa, the operation current exceeds 5000 A on a single electrode, which improves the testing ability of the segmented arc heater.