A large system of sparse linear and nonlinear algebraic equations is the typical form of mathematical models of process design and steady state process simulation. Successive substitution is an efficient solution strategy for this type ot models in that the equations can be nonlinear and an output is available at any step of calculation. Besides

it needs less storage space and shorter CPU time. However

the design variables(if the number of variables is larger than that of equations)

iteration variables

output set and the substitution sequence must be first determined before iteration begins. A simple and convenient method of rearranging the occurrence matrix of the system is proposed in the paper. After rearrangement

the iteration variables are firsty determined

and subsequently the output set and design variables are determined

so that a feasibie solution routine of the system ot equations is established.