Aworkable particle bombardment-mediated common wheat transformation system has been developed for generating transgenicwheat free from selectable marker genes and vector backbone.The aim of this study was to assess the influence of modifying the ratioon the chance of transformation and expression of the non-selectedGUS gene and co-transformation to optimize and develop an efficientparticle bombardment-mediated common wheattransformation system.A combination of GUS cassette and herbicide resistancegene was used to select stable putative transformants.Several combination have been proposed,whole plasmid pAHC25 as the reference.Six independent co-transformation experiments were carried out,using the corresponding minimal gene cassettesbar or pAHC20 andgus at different mole ratio were transferred to wheat immature embryos.Kenong 199 asthe recipient plant.Fifty six independent transgenic lineswere generated.The results of the study showed that there were no positive correlationbetween transient expression and stable transformation have been found.However,the final transformation of non-selectedtransgene expression efficiency was significant difference,the highest transformation efficiency is the combination using minimal constructs at the mole ratio 1:2,transformation efficiencies of whole plasmidwasslight lower than minimal constructsco-transformation at a mole ratio of 1:2,while it was significant higher than minimal constructsco-transformation at a mole ratio of 1:1 and 1:3.Stable integration,expressionand inheritance of foreign genes were confirmed by GUS assayandsouthern blot analysis.Positive transgenic lines displayed normal morphologies.This wheat transformation system may provide usefulinformation for future transformation study.