This study explores the impact of English learning experience on German learning from the behavioral perspective. The purpose of the study is to prove that the first foreign language learning experience helps other foreign language learning. In the present study, freshmen students of the German Department of Tamkang University were selected as the research subjects. The qualitative and quantitative interview was conducted to investigate the major difficulties in the process of learning German, the influence of English on the German language and the degree of English proficiency and the German level of relevance. Quantitative results show that beginners' English proficiency has a moderate positive correlation with their German learning effectiveness, but the perception of English has no effect on German learning. However, according to the results of the interview, all participating respondents indicated that English has an impact on the process of German learning. In the beginning phase of German learning, English disturbed German, especially for spelling and pronunciation. After learning for a period of time, English turns to have positive effect, especially those with better English proficiency thought that English learning experience helped them for German grammar and sentence structure.