Abstract: Described in the essay are the main technological parameters of the 14-stand slight-stretch reducing mill driven by a centralized differential transmission system，and focused on are the critical design elements of the drive system such as velocity curve，main drive gear ratio，and calculation and mating of the superposition ratio，etc.Also elaborated are the design tips of other elements concerning the main drive system，including rigidity of the gear box，the lubrication system，the gear strength and so on.The results from relevant calculations and operation practice show that the main drive system of the slight-stretch reducing mill as designed is capable of meeting the velocity scheme as required by the manufacturing process，having resulted in satisfactory operation effectiveness，and being worth using as reference for future newly-built mills，and mill upgrades as well.