Objective　To explore the mutation characteristics of HB Quong Sze. Methods　A 5-year-old boy was suspected with thalassemia and had a hemoglobin of 113 g/L, a mean corpuscular volume of 66.5 fl and a mean hemoglobin content of 21.6 pg. The PCR was used to detect 3 common forms of alpha-thalassemia and 17 beta-thalassemia genes , and no abnormalities were found. Then the next-generation sequencing was used for gene detection and verification. Results　A heterozygous mutation of α thalassemia, HBA2 c.377T > C, was detected in the patient, which came from the father, and HB Quong Sze was confirmed. Conclusion　Next-generation sequencing can diagnose HB Quong Sze type thalassemia which has no abnormalities in conventional genetic testing.