Abstract:The essence, significance and relationship of Polybasic Acid or Polybasic Base titration conditions were revealed with the titration curve. The findings showed that: K _i/K _i+1is the determining factor of stepwise titration and the primary indicator that influences the titration jump; while c _spiK _iis the key which determines the jump value when K _i/K _i+1is enough large. The decision procedure of before-titration is: first, to determine whether the K _i/K _i+1of the measured object is greater than or equal to 10 ⁵, so as to see whether the stepwise titration is applicable; then it is to determine whether c _spiK _iis greater than or equal to 10 ^-9, so as to see whether accurate titration can be directly applied under the current conditions.