Idiom: "dead-end job"  

Definition:

a job that doesn't lead to anything

Examples:

1) Working as a cashier at McDonalds is considered a dead-end job.

2) Sam finally quit his dead-end job to start his own business.

中文解释： http://www.youzienglish.com/main/idiom_of_the_day/dead_end_job/cn/