Which Bus can take me to Big Wild Goose Pagoda from Northwestern Polytechnical University(Xi Gong Da

This university has more than one campus. Which one do you leave from?
Anyway, if you mean the campus at West Youyi Road, bus no. 24, 21 oe 521 can take you to the Big Wild Goose Pagoda.
If you mean the Chang'an Campus, you can take bus no. 916 to Xixie Qilu Station. Then transfer to bus no. 34 or 400 to your destination.