Abstract: In moral dilemmas, bilinguals exhibit a higher rate of rational decision-making when using a foreign language compared to their native language. This phenomenon is known as the "moral foreign language effect". However, prior studies have predominantly relied on offline measures, providing limited insight into the effect’s online processing dynamics. Therefore, this study employed self-paced reading, an online measurement method, to investigate the moral foreign language effect and its processing mechanism in Chinese English learners' sentence comprehension, incorporating foreign language proficiency as a variable for a multidimensional examination of the foreign language effect. Results showed that at the critical words both moral and semantic violations required longer response time compared to correct sentences, with semantic violations taking longer response time than moral violations. More importantly, an interaction between violation type and group emerged at the sentence-final words. In the native language context, response time for moral violations was significantly longer than correct sentences. In contrast, in the foreign language context, there was no significant difference in response time between moral violations and correct sentences, irrespective of foreign language proficiency. These findings demonstrate that 1) Chinese EFL learners exhibit the moral foreign language effect during natural language comprehension, which can extend to everyday moral violations and is not modulated by foreign language proficiency; 2) the moral foreign language effect may be caused by weakened emotional processing. Specifically, using a foreign language diminishes the emotional aversion triggered by moral violations, leading to greater tolerance in moral judgment. This suggests that, in daily life, we should take a dialectical view of the impact of foreign languages.