Multi-agent applications utilize the advanced capabilities of large language models (LLMs) for intricate task completion through agent collaboration in a workflow. Under this situation, requests from different agents usually access the same shared LLM to perform different kinds of tasks, forcing the shared LLM to suffer excessive loads. However, existing works have low serving performance for these multi-agent applications, mainly due to the ignorance of inter-agent latency and resource differences for request scheduling. We therefore propose Kairos, a multi-agent orchestration system that optimizes end-to-end latency for multi-agent applications. Kairos consists of a workflow orchestrator, a workflow-aware priority scheduler, and a memory-aware dispatcher. The orchestrator collects agent-specific information for online workflow analysis. The scheduler decides the serving priority of the requests based on their latency characteristics to reduce the overall queuing. The dispatcher dispatches the requests to different LLM instances based on their memory demands to avoid GPU overloading. Experimental results show that Kairos reduces end-to-end latency by 17.8% to 28.4% compared to state-of-the-art works.