Continuous assessment (CA) is believed to have great potential for improving learning in higher education. Students' beliefs about CA are a determining force for optimising CA's formative potential. This study explored 27 Chinese undergraduates' beliefs about CA functions in their college English course through individual semi-structured interviews. The findings reveal that more than half of the participants noticed the judgemental function of CA. The majority valued CA as an external force that motivated them to learn. Fewer than half believed that CA informed their learning. It is argued that this perceived strong extrinsic motivational function and weak informing function might constrain the participants' sustainable learning improvement. The findings show that the participants' beliefs about CA functions were ecologically rational. The macrosystem (China's education system and examination culture) and exosystem (university assessment policy) enhanced the participants' recognition of CA as a motivator. Further, the microsystem (lecturer feedback and grading practices) and chronosystem (students' transition from high school to university) contributed to their lower awareness of CA as a useful feedback source.