Affective factors are seen to play an important role in second language acquisition and foreign languages teaching. It has been proved that the positive, confident and relaxing mental state can facilitate the process of second language acquisition;on the contrary, those negative factors such as depression, inhibition and anxiety, etc, will impede the process of acquisition. Based on the introduction to .Krashen＇ s “Affective Filter Hypothesis” and some other affective factors in second language acquisition, this paper provides some advice for the foreign languages teaching.