Abstract：In light of the choice set theory and the default effect, this study proposes that when donation amount is set as the default option, the degree of the default amount (high vs. low) negatively affects donation intention. As compared to a low-amount default option, when individuals face a high-amount default option, their donation intention becomes lower. Further, this study posits that the perceived inference of manipulation mediates the process of how the default option of donation amount affects donation intention. In addition, individuals’ moral identity moderates the aforementioned process. We conducted three experiments to test our hypotheses. Specifically, the first study employed a 2 group (default option: high vs. low amount) between-subjects design to test the main effect. In a college lab setting, subjects first read a call-for-donation message introducing a fictitious donation request (to build libraries) from a fictitious online charitable organization. Then subjects were presented with four options of the amount of money they may donate, with the default option set at ￥12 in the high-amount condition and ￥5 in the low-amount condition. Finally, their donation intention was measured by intention and actually donation behavior. Results show that the high-amount (vs. low-amount) default option leads to lower donation intention, confirming H1. Study 2 was to test the mediating role of the perceived inference of manipulation by conducting a 3 group (default option: high-amount vs. low-amount vs. no default option) between -subjects design. Study 2 recruited subjects from a large online research platform. The procedures were identical to experiment 1 except that the call-for-donation message was different. Finally, the perceived of inference of manipulation, donation intention, emotion, and reactance were measured respectively. Study 3 was to test the moderating role of moral identity by employing a 2 (default option: high-amount vs. low-amount) × 2 (moral identity: high vs. low) between-subjects design. Results indicate that when individuals are high in moral identity, the default option of amount elicits no different impact on donation intention. However, when individuals are low in moral identity, the high-amount (vs. the low-amount) default option leads to lower donation intention. Supporting our hypotheses, the high-amount (vs. the low-amount) default option leads to lower donation intention, with the perceived inference of manipulation playing the mediating role. Besides, moral identity moderates the relationship between the default option and donation intention. We point out that the default option of donation amount has triggered a backfire default effect instead of a default effect in a non-economic-choice setting. Findings have contributed to the area of (backfire) default effect, choice set theory, and donation. Managerial implications are also addressed.