Nudge improves decisions about health, wealth, and happiness by providing a simple, low-cost option framework. Default options, a widely discussed and used behavioral intervention, influence people's choices by presenting an option that has been chosen in advance for decision makers. Default options have shown to be effective in many areas of application (e.g., organ donation, retirement plans, among others). Considering that charity fundraising is costly and time-consuming, and few studies have examined the effect of default option on charity fundraising, we conducted three experiments to explore whether the strategy of setting default options could promote people’s donation behavior. In Experiment 1, we examined whether defaulting the option of “donating” or “not donating” a CNY 5 participation fee affected donation behavior. The participants were assigned randomly to one of the two conditions: defaulting to be a donor (DD) and defaulting not to be a donor (DND). In Experiment 2, we examined whether setting different amounts as defaults could affect donation behavior. We set CNY 10, CNY 15, CNY 20, CNY 25, and a blank cell (donors could decide whatever amount they wished to donate) as default donation options in different conditions. In Experiment 3, we intended to examine whether setting the default option at a larger amount would increase the average donation amount. The option settings were similar to Experiment 2, but the blank cell was removed, and CNY 0 and CNY 5 options were added, where choosing CNY 0 meant that participants chose not to donate and CNY 5 was used for maintaining the gradient of donation amounts and became the minimum donation option. Participants were randomly assigned to one of the three groups to make donation choices: control group (no defaulting), “default donation CNY 5” group in which the lowest donation amount was set to be the default, and “default donation CNY 25” group in which the highest amount was set to be the default donation. The results of Experiment 1 demonstrated that the donation rate and donation revenue were higher when “Donate to UNICEF” other than “Keep it for yourself” was set as the default option. The results of Experiment 2 showed that the strategy of setting default options generally promoted participants to select the default options, but not the average donation amounts. Experiment 3 found that setting the default at a high amount could bring a higher average donation amount than not defaulting or defaulting at a lower amount. Experiment 3 also found that the probability of selecting the default options increased, but the donation rate neither increased nor decreased. The overall results of the three experiments showed that the defaulting strategy could effectively promote the donation behavior of decision makers. Fund-raising collects hundreds of billions of RMB in the mainland of China annually. However, it is an arduous and costly effort. Our studies demonstrated that a defaulting strategy could raise donation revenue without adding extra costs through defaulting the donation option or defaulting the largest amount, which especially applies to increasingly popular Web-based fund-raisers.