Error is a critical factor affecting the working performance of high-precision gear drives. This paper focuses on studying the impact of errors on the meshing performance of a novel drive applied in robot joints with an integrated structure of drive, transmission and support. The novel drive is named the Inner Gear Plane Enveloping Worm Drive (abbreviated as IPE drive), which is characteristic by several advantages, including a large single-stage reduction ratio, strong carrying capacity, high precision, small size, simple structure, long service life and power-off protection through mechanical self-locking. Therefore, it is a novel high-performance drive with potential applications in robot joints. In this paper, we systematically studied the impact mechanism of errors around the IPE drive to safeguard its performance. The main contents are shown as follows: (1) Taking machining errors and assembly errors into account, the coordinate frame system of IPE drive including errors was established by the moving coordinate method. (2) Based on gear meshing theory and differential geometry, equations of contact lines, boundary curves, etc. under the coordinate frame system were derived to establish the meshing theory system of IPE drive including errors. (3) The effects of machining errors and assembly errors on the meshing performance of the IPE drive were analyzed to guide the design and manufacturing in theory. This study is significant in providing a foundation for applying an IPE drive in the novel high-performance robot joint.