The electric field intensity and space charge density are important parameters for gas discharge, and the study of the relationship between them not only helps to better understand the mechanism of corona discharge but also provides a reference for insulation margin design for power equipment. In this article, a space charge measurement platform based on the acoustic pulse method is constructed, and in this way, the distribution of space charge density in the corona cage can be obtained. In addition, corona discharge characteristics (including onset characteristics and electric field distribution) are obtained based on theoretical calculation and experimental measurement, and then the correlation mechanism between space charge and field intensity under dc voltage is established. The results show that when corona discharge occurs, the space charge density is positively correlated with the onset voltage and negatively correlated with the onset electric field, and the space charge is also negatively correlated with the surface electric field intensity around the wire surface. However, the space charge density gets bigger with the increase of spatial electric field intensity in the corona cage. The above research results can reveal the correlation mechanism between space charge and electric field intensity more accurately, which is of great significance for the in-depth study of the corona discharge mechanism and air discharge characteristics.