The secondary gun probe can be used to monitor two states in the steelmaking process. In the middle stage, it can be used for monitoring the carbon and temperature contents and collecting samples; in the final stage, it can be used for monitoring the states, which is also known as the endpoint inspection, including temperature measurement, oxygen measurement, sampling and carbon content calculation. The endpoint components are obtained from the sampling spectrum test, and the process references are provided from the interim test. The endpoint test is used to examine the steelmaking state and then realize the automatic steelmaking process.