Objective To analyze the coincidence of the patients with capillary electrophoresis hemoglobin A 2 increase with defi-nitely diagnosed beta thalassaemia and to investigate its application value in the diagnosis of beta thalassaemia.Methods Two hundreds and sixty outpatients and inpatients with hemoglobin A 2 increase in our hospital from May 2014 to May 2015 were per-formed the genetic testing.Results Among 260 patients with hemoglobin A2 increase ,beta thalassemia gene mutations were detec-ted in 257 cases ,the coincidence rate reached 98.85% ,and the common 17 beta thalassemia gene mutations were not detected in the other 3 cases ,follow-up further detection of rare beta thalassaemia gene and beta globin gene sequencing was performed ,1 case of SEA-HPFH βdeletion type was found ,1 case was Taiwaneseβdeletion type and 1 case was Codon 89-93(-AGT GAG CTG CAC TG) heterozygous mutation ,it was verified that 3 cases of hemoglobin A2 increase without detecting 17 kinds of common beta thalassemia gene mutations were still beta chain mutation occurrence or big fragment deletion.At the same time ,among 257 speci-mens of beta thalassemia gene mutations ,42 cases were compound alpha thalassaemia ,accounting for 16.34% of beta thalassaemia. Conclusion Capillary electrophoresis hemoglobin A2 increase can provide a fast and accurate basis for beta thalassemia diagnosis , but which can not rule out the possibility of compoound alpha thalassaemia ,when the patient's hemoglobin A2 is increased ,alpha and beta thalassaemia genetic diagnosis should be simultaneously carried out.