This paper presents a way to quantitatively characterize switching processing features by information theoretical analysis. The analysis concept is based on understanding that a switching processor is an information processing machine for obtaining input information from subscribers and for sending output information to a speehpath network. In order to convert the input information to the output information, the switching system must choose a suitable internal action out of many possibilities, namely, the system has some entropy in making a decision on its response to the input information. The internal processing is considered, therefore, to contribute to decreasing the entropy. Based on the above comprehension on the switching system, an information processing evaluation principle and some parameters for control structure design are proposed. Using those parameters, partition and assignment way of processing amount to control stages or to switching functions such as input, internal and output processing are decided. Those parameters can be used also as measures of system flexibility or service variety and speechpath network control ease. Example figures of those parameters are given by analysis of a 7 digit rotary dialing intra-office call processing in a large scale stored program controlled model switching system. The values obtained can be considered to indicate the information processing level in the present switching system and may be also used to design quantitatively call processing capacity of a switching system and simultaneously to show an objective to be surpassed in future switching system development.