With the change of market supply and demand structure,discrete manufacturing industry urgently needs market-oriented reform.Taking T company as an example.This paper analyzes the mechanical assembly of cotton spinning locomotive head by using lean production theory and VSM as a tool.It is found that there are some de-fects,such as unbalanced production scheduling between processes,long mold change cycle of bottleneck proces-ses,low on-site lean level and waste of processing technology.Based on this,i.e.technologies such as Kanban pull,SMED rapid die change,ESCR law and process improvement are used to optimize and draw the future map of value stream.This paper creatively introduces the lean production theory into the mechanical assembly of cotton spinning head to achieve the purpose of reducing cost and increasing efficiency,which has a certain reference significance for the manufacturing and optimization of discrete mechanical assembly.