Tooth profile modification and manufacturing error of cycloidal gear are the key factors that affect the transmission accuracy of cycloidal pinwheel. In order to analyze the transmission error of the cycloid gear under the multi-factor comprehensive effect, based on the theory of gearing and coordinate transformation, an error analysis model of the cycloidal pinwheel meshing pair under the comprehensive effect of multiple factors was obtained by constructing the tooth profile equation of the cycloid gear with the comprehensive factors such as tooth profile modification, machining error and assembly error taken into consideration. The model can be used to analyze and calculate the combined transmission errors of the cycloid pin gear under the comprehensive effects of tooth profile modification, machining and assembly errors. The influences of various error factors and multiple factors on the transmission error were analyzed. The results show that the cumulative pitch error has the greatest influence on the transmission error, followed by cycloidal profile error and assembly error; the pin radius error and the pin position radius error have the least influence on the transmission error.