Quantum dot is a typical nano functional device, which has a very attractive prospect in biotechnology, semiconductor technology, quantum optics and other fields. In this paper, we construct a cavity containing a two-level atom to simulate a nano cavity coupling a two-level quantum dot, and study the electrical transmission in the cavity. We solve the transfer function of a single electron and obtain the formulas of transportation and reflection. By adjusting the intrinsic properties of the cavity and the atom and coupling between them, we study the transmission characteristics of a single electron in the cavity and understand the role of the two-level atom and the cavity in the electrical transport. The results can provide some theoretical support for quantum control of the electron transport in a nano device.