In order to solve the problems such as big residue，nozzle ring blockage，pulverizer capacity shortage and so on，it was proposed to upgrade the nozzle ring of medium speed coal mill. The number of the nozzle ring was distributed reasonably，and the streamline shape of the blade was optimized，the flow area was guaranteed. The bottom of the nozzle ring was outward in tilt angle and was designed as horn. The primary air was split into two parts and form the condition that blowing upward and broadwise. The texture of the nozzle ring was altered，KmTBCr20 was used and the abrasion loss was reduced. The adjustable damper device was set to compensate the abrasion of the coal mill. The pulverizer capacity was improved，the grinding ability was increased，the wearing capacity was reduced and the service life was extended. Meanwhile it meet the needs of mixed lignite and the generating cost was reduced.