The concept of bond blocks has been suggested for description of the f
ormation kinetics and structure of polymer networks. The full set of c
oncentrations of bond blocks provided full description of the polymer
system. The relations between the concentrations of bond blocks and of
macromolecules are derived. The law of mass action for the bond block
s is formulated. It is shown that in certain cases it is possible to r
eplace part of differential equations describing the kinetics by the a
lgebraic ones. Examples of applications of the concept of bond blocks
are given.