Based on related bilingual event-related potentials (ERPs) research, the article reviews and analyzes the factors influencing second language (L2) syntactic processing. After a brief introduction to ERPs and monolingual ERP research, five findings from recent ERP research are explored. Firstly, age of acquisition (AoA) have impacts on L2 processing, but it is highly controversial. Secondly, ERP effect changes qualitatively with the development and proficiency level of L2. Thirdly, similarity between L1 and L2 can decide whether L2 learners can reach to a nativelike processing signature. Fourthly, learning context is also an important factor in L2 syntactic processing, and implicit or explicit context of learning can lead to different results. Fifthly, syntactic complexity can also be an affecting factor, and L2 learners can not processing highly complex syntactic structures as L1 learners do. At last, the article summarizes the above five factors and provides implications and suggestions for future ERP studies.