You should include a directive like this in your nginx configuration file (inside the block of your server configuration):
limit_rate 150k;
This limits the speed of transmission of the answer to client. It works as a limit for each connection, not for the total server transfer rate. (Maybe you can adjust max_clients = worker_processes *worker_connections as
a work-around to limit total transfer.)
Take a look at nginx documentation for limit_rate. There is also a limit_rate_after directive
that is useful to set this limit only after download exceeds certain size.
原文：http://blog.csdn.net/hellochenlian/article/details/44923443