A key factor of success for modern public library service systems is human resources. But the current research on library human resources focuses mainly on management and pays little attention to the supporting of continuous library development. Since 2015, with local policy and regulation support, Guangzhou has been promoting public library services and building a"City of Libraries". However,human resources is a challenging issue. A survey of 2 municipal libraries,11 district libraries and 43 sub-district libraries in Guangzhou has been conducted to reveal the current status of library human resources. By comparing to the needs of a modern public library service system,this paper identifies three key challenges in human resources,i.e. insufficient number of staff, level of professionalism not matching the expectation, and inadequate opportunities of continuing education.