Background & objective: Pompe disease is a rare inherited neuromuscular disorder. Due to the high cost of enzyme replacement therapy (ERT), most of adults with late-onset Pompe disease (LOPD) who received ERT used the medication with insufficient doses in China. This study aimed to compare the change in quality of life (QoL) between adults with LOPD receiving under-dose ERT and no ERT. Methods: A retrospective matched cohort study was conducted among adult patients with LOPD in a nationwide Pompe registry in China. Patients who were not using ERT at baseline and before were included. The case group were those who received under-dose ERT during the 14-month follow-up; the control group were those who received general care. Under-dose ERT was judged by the ratio of actual vitals patients used divided by the indicated vitals patients should use (<80%). Case and control patients were matched with a ratio of 1:2 based on age, sex, dependence on devices, and geographic location. QoL was assessed by the SF-12 and EQ-5D-5L. Results: Eleven cases with under-dose ERT and 22 controls without ERT were included. In paired sample analyses, patients with under-dose ERT had a significant improvement in an overall measure of health status, i.e. EQ-5D VAS (38.7 vs. 62.8, p=0.018). Using the changes of QoL scores between baseline and follow-up as outcomes, the multiple linear regression analyses indicated that under-dose ERT was not significantly associated with change in SF-12 physical or mental component score, and EQ-5D index score compared with the control group (p>0.05), while it was positively associated with change in EQ-5D VAS (β=20.55, p=0.020). Conclusions: Under-dose ERT significantly improved the overall health state among users, however, this improvement was not captured by the sub-dimension measure on physical or mental QoL. A Pompe disease-specific QoL tool is needed to better monitor change in QoL.