This study aimed at applying key-image pictured-based approach to teach Chinese-characters for Chinese as foreign language learners in the environment of online classroom. It was a qusi-experiment design. 65 ages 10-12 school children from an elementary school of southern California participated in the research, 32 students in the experimental group and 33 pupils in the control group. The intervention of key-imaged pictured-based approach of teaching Chinese-characters in the online classroom was applied to the experimental class over a 15-lesson period in 3 months. The control class accepted Chinese language class without the intervention in the regular classroom in the same period of teaching schedule. The result of a detailed one-way ANCOVA demonstrated that the intervention of key-imaged pictured-based approach of teaching Chinese-characters with online environment in the experimental class contributed significant grow in vocabulary skills.