From the perspective of product uncertainty, the effect of product type, product price and sales on buyer’s online payment method choice was explored with a 2 price levels (high vs. low) × 2 sales levels (high vs. low) × 2 product types (experience vs. search) within-subjects eye-tracking experiment. Thirty voluntary participants from Zhejiang University participated in the experiment. The determinants of payment method choice were examined in three levels data including observable behavior data, attention eye-tracking data, and psychometric cognitive data. Repeated measures ANOVE and logistics regression indicated that product uncertainty and price were the two main determinants of online payment method choice. Pay-after-delivery was more likely to be chosen when price or product uncertainty was high. However, sales had no significant effect on the choice. The analysis of eye-tracking data, including dwell time and duration before on AOI-price and AOI-sales, found that buyers first paid attention to and had more cognitive effort on the price than sales. This study extended the theory of product uncertainty, and provided cognitive processing of information behind online payment method choice. The results of this study can help the online sellers optimize the service of payment, finally improving the development of e-business.