With the model that the number of repeating units of the homologous series varies successively, two fundamental relationships have been developed: P=a+bn and P=c+kln n=a/n+b Where a、b、c、k all refer to the constants, n to the number of repeating units, P tothe properties for homogolous series. Generally, additive type properties conform to thelinear relationship, adn the structural - type properties and condened - type properties tothe homololgous logarithmic linear relationship.

Key words: HOMOLOG, CHANGE LOW, PHYSICAL CHEMISTRY PROPERTY, HOMOLOGOUS LINEARITY RULE