Abstract:This paper briefly introduces several test indexes for ultrasonic flowmeter , and preliminarily interprets the relationship between the sound velocity deviation in GB/T 30500-2014 "ultrasonic gas flow meter performance online audit-method using speed of sound checking" and the verification. The flowmeters that have been in use for six consecutive years (statutory longest inspection period) qualified, unqualified flow pattern, unqualified signal quality of flowmeters and unqualified sound velocity deviation are selected to track the results of their subsequent real-flow verification (additional sound velocity verification if necessary), and analyze the various evaluation indexes and flowmeters that are being inspected in use. The relationship between measurement performance and the possible reasons for unqualified indicators are further analyzed, and suggestions for investigation are given as far as possible. It is expected that the analysis of test results in use can provide reference for the field use of ultrasonic flowmeters.