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+1 is the determining factor of stepwise titration and the primary indicator that influences the titration jump; while c_spi K_i is the key which determines the jump value when K_i/K_i+1 is enough large. The decision procedure of before-titration is: first, to determine whether the K_i/K_i+1 of the measured object is greater than or equal to 10⁵, so as to see whether the stepwise titration is applicable; then it is to determine whether c_spi K_i is greater than or equal to 10^-9, so as to see whether accurate titration can be directly applied under the current conditions.