German Social Democratic Party has experienced a half century of ups and downs and profound changes have taken place in social structure. This change has a profound influence upon the transformation of the Social Democratic Party and its nature has evolved from “Class Revolutionary Party” to “Parliamentary Reform Party”, from “People's Party” to “Catch-all Party”，from the pursuit of “institutional socialism” to “value socialism”. The overall trend is the SPD’s “non-working class” and “non-ideology”. The SPD has gradually changed from a revolutionary party fighting for the interests of the working class to an election party aiming to participate in public affairs or hold power.