Anthropomorphic design is a common method in brand building, marketing communication or product design, such as being used for the brand mascot. Generally speaking, anthropomorphic design in marketing can increase perceived intimacy, purchase intention or product evaluation, among others. However, there was insufficient attention in research on the possible negative effects of anthropomorphism. Focusing on food advertisements, this study tried to identify the mechanism of inappropriate anthropomorphic design in advertisement, which may lead to consumers’ negative emotional response and attitude toward advertisement. We conducted three experiments to investigate this speculation. The data of Study 1 was collected from 80 undergraduates. Participants in Group 1 saw the anthropomorphic advertisement while Group 2 saw a non-anthropomorphic advertisement, following which both groups responded to questionnaire items on the manipulation check of anthropomorphism, attitude toward advertisement and guilt. Study 2 and 3 further investigated the boundary effect of the authenticity of humanity. Study 2 manipulated authenticity by anthropomorphizing different objects in the advertisement. Participants in Study 3 were presented with different sets of science material on plant, which influenced their perception of humanity authenticity. The data of Study 2 and 3 were collected from 135 and 105 undergraduates. Our experiments showed that inappropriate anthropomorphic design in food advertisement generated illusions of “eating people”, and made consumers feel guilty. Guilt is a kind of self-conscious emotion, which involves negative feelings about a specific behavior or action taken by the self. So, anthropomorphic design in food makes “eating” a hurtful behavior, which subsequently makes consumers feel guilty. The results showed that the negative effects of anthropomorphic design on attitude towards advertisement were mediated by the guilty feeling. Furthermore, this effect only happened when perceived humanity authenticity of food anthropomorphic design was high. When consumers did not believe the anthropomorphized object had the ability to think (authenticity of food anthropomorphic design is low), then it would not lower the positive attitude towards the advertisement. As a result, the negative effect would only happen when pigs but not when meat balls were anthropomorphized (Study 2), and when participants read materials indicating that even mushroom could feel the pain (Study 3). This study filled the gap of the negative influence of anthropomorphic design by exploring the mechanism of negative emotion (guilt) and authenticity. Furthermore, past research usually focused on companies or marketing materials, however, this study focused on the view of consumers’ wellbeing. The studies provide important implications for food advertising.