One of the important subjects about protection systems for offshore plaforms is that of its Designing and monitoring cathodic protection. In the early years Dwight equation and those simillar to it were used for designing cathodic protection system. As anode coerrode, their dimentions change. In addition sea conditions such as temprature change, salinity variation, Current speeds of water and calcareous deposits formations on underwater parts of offshore plateformes are all variables, that make, Dwight and simillar equations of no use for answering problems concerning design of cathodic protection systems. Today computer modeling is succestully used for designing and monitoring cathodic protection system. In this type of process potential distribution at each part are obtained by measuring potentials of only limited number of points of the offshore plateform. In this article we not only discuss the above subjects but also we talk about a technology for monitoring cathodic protection systems in offshore platforms, equipment used for this purpose and manipulation mathematical calculation used for cathodic protection system. Also in this article methods and related equipment used as data acquisition system, its classifications, mathematical calculation and finally the application of computer in this regard, are all discussed