As one of the regulators of cationic concentration in cells, potassium channels play an important role in the depolarization and repolarization of nerve cell. KcsA (K ⁺conduction and selectivity architecture) channel is simple and has the commonness of potassium ion channel, which is often used as a template for potassium channel research. In this paper, Brownian dynamics (BD) method is used to simulate the electrical characteristics of the actual KcsA potassium channel systematically. The potential mean force (PMF) of ions in the channel under electrostatic field, the current-voltage characteristic curve of symmetric solution and asymmetric solution, the ion concentration distribution curve in the axial direction of the channel, and the conduction-concentration curve are obtained. The results show that the selectivity filter region of KcsA potassium channel blocks the passage of Cl ^–basically, showing a special selection characteristic of the passage of K ⁺, that its current-voltage curve presents a basically linear distribution, and that the conductivity-concentration curve presents a trend of first increasing and then flattening. The basic characteristic is consistent with the experimental phenomenon. In addition, the influence of the THz field on the channel K ⁺current is also simulated and analyzed. Compared with applying only the same amplitude electrostatic field, the selected terahertz field of 0.6 THz, 1.2 THz, and 5 THz can reduce the PMF by affecting the interaction potential energy between ion pairs, thereby increasing the K ⁺current. The research in this paper not only deepens the understanding of the regularity of KcsA potassium ion channels, but also provides a new idea for studying other types of ion channels and the influence of terahertz field on the characteristics of ion channels.