Agents powered by large language models have shown remarkable reasoning and execution capabilities, attracting researchers to explore their potential in the recommendation domain. Previous studies have primarily focused on enhancing the capabilities of either recommendation agents or user agents independently, but have not considered the interaction and collaboration between recommendation agents and user agents. To address this gap, we propose a novel framework named FLOW, which achieves collaboration between the recommendation agent and the user agent by introducing a feedback loop. Specifically, the recommendation agent refines its understanding of the user's preferences by analyzing the user agent's feedback on previously suggested items, while the user agent leverages suggested items to uncover deeper insights into the user's latent interests. This iterative refinement process enhances the reasoning capabilities of both the recommendation agent and the user agent, enabling more precise recommendations and a more accurate simulation of user behavior. To demonstrate the effectiveness of the feedback loop, we evaluate both recommendation performance and user simulation performance on three widely used recommendation domain datasets. The experimental results indicate that the feedback loop can simultaneously improve the performance of both the recommendation and user agents.