Background: Recently, a study revealed that people liked others significantly more than they estimated that others liked them. Thus, the study found that people tended to underestimate how much others liked them, a phenomenon the authors called the Liking Gap. However, the logic and testing of the study existed unclear nature. In order to show whether people underestimate the positivity of impression they left on others, we directly compare the estimate of the impression we left on others with others' actual impression of us, which make the logic clear. Besides, we explored the new findings with regard to the mechanism of the effect. Methods: Based on this idea, in study 1, we explored whether there is indeed a negative deviation effect in the estimate of the impression people left on others in short interpersonal communication. In study 2, we investigated the potential psychological mechanisms of that effect. Results: In Study 1, the results revealed that people estimated that others liked them significantly less than others actually liked them. That is, a negative deviation effect did occur, and even if people were clear about their liking for others, the effect still existed. In Study 2, we provided evidence that a negative deviation effect existed not just because people are too focused on their own-negative thoughts in conversational performance but rather because people had a psychological defense towards others in their first communication. Conclusion: People significantly underestimate how much they are liked and its reason is that their psychological defense towards others in their initial communication. The results of the study are beneficial for people in social interaction and provide them with new ways of thinking in interpersonal communication and mutual contact.