The interface configuration command is: srr-queue bandwidth limit.
I hope this helps.
The command recommended by Massimiliano will definitely give you what you want, however it's best to understand all other QoS components in the 3750, so check out the full document on the subject at:
You need rate-limit
rate-limit output 128000 14000 14000 conform-action transmit exceed-action drop
i think this can only limit the traffic to 1M because the minimum parameter is 10 percent, my question is: how to configure lower than 1M, say 128K?