形容人跑得快的英语句子有很多，以下是一些常见的表达方式：

1. He runs as fast as a hare.

2. He runs as fast as an arrow.

3. He's a fast runner.

4. She can really move on the track.

5. He's got some serious speed.

6. She's quick on her feet.

7. He's a fleet-footed runner.

8. She's a lightning-fast sprinter.

9. He runs quickly.

10. She runs quickly.

11. He is running at top speed.

12. He is running at a breakneck pace.

这些句子都可以用来形容一个人跑得快，具体使用哪个句子可以根据语境和需要强调的程度来决定。例如，如果想强调速度的极限，可以使用“as fast as a hare”或“as fast as an arrow”；如果想强调某人在跑步方面的能力，可以使用“fast runner”或“fleet-footed runner”；如果想描述正在进行的快速跑步，可以使用“running at top speed”或“running at a breakneck pace”。