Prospective memory is an ability to successfully perform an intention, referring to the memory of a planned event in a specific situation or at a specific time in the future. Prospective memory can be divided into event-based prospective memory and time-based prospective memory. Event-based prospective memory includes prospective component and retrospective component. Prospective component is the observation and recognition of target clues, and retrospective component is the extraction of future intention. Previous studies have shown that cognitive load, encoding modes would affect the prospective memory performance of the participants. However, there are still different views about whether different encoding modes have influence on prospective memory. The influence of different encoding modes on prospective memory under different cognitive load has not been determined. Therefore, this study explores the effects of cognitive load and encoding modes with simple intention content on the prospective memory and its components through two experiments. In experiment 1, we adapted 2 (cognitive load: high, low) × 3 (encoding modes: standard encoding, implementation intentions encoding, writing encoding) mixed design. During the experiment, the participants were supposed to complete two tasks at the same time. The ongoing tasks were divided into 1-back task and 2-back task, which correspond to low and high cognitive load. The encoding mode of prospective memory tasks were divided into standard encoding, implementation intentions encoding and writing encoding. Experiment 1 results showed that under low cognitive load, prospective memory performance was better than that of high cognitive load conditions. Under the implementation intentions encoding and writing encoding, the correct rate of prospective memory were significantly higher than that of standard encoding, and there was no significant difference between the implementation intentions encoding and writing encoding. In experiment 2, we adapted 2 (cognitive load: high, low) × 3 (encoding modes: standard encoding, implementation intentions encoding, writing encoding) mixed design. At the same time, on the basis of experiment 1, we used the experimental separation method to separating the two components and tried to probe how the cognitive load and encoding mode affect the prospective component and retrospective component performance of the participants. The results of experiment 2 showed that under low cognitive load conditions, the performance of prospective components were better than that of the high cognitive load conditions. The correct rate of the prospective components under implementation intentions encoding and writing encoding was significantly higher than that of the standard encoding. And there was no significant difference between the former two encoding modes. Different cognitive load and encoding modes had no significant effect on the retrospective components. The results show that in the case of simple intention content, low cognitive load makes for the successful execution of prospective memory because of the higher successful rate of prospective components. What’s more, implementation intentions encoding and writing encoding can promote the prospective memory performance by promoting the extraction of prospective components.