The cyclic functional method is one of the methods for analysing energysaving in the steam cycle of a power plant. The key point of said method is calculation of water intake coefficient for the unit. Starting from conventional heat balance

a matrix calculation model for water intake coefficient of the unit has been deducted and established

the rules of filling up the matrix being simple

having clear and definite physical meaning

as well as having features for universal purpose

and being easy to be computerized. Taking BΠT502 type unit as example

the suitability of the said matrix model has been discussed

and the effectiveness of the said method being explained.