Different from existing methods of software complexity measure such as Halstead s Software Science, McCabe s Cyclomatic Complexity, and Chidamber and Kemerer s definition of six metrics, this paper provides a new method to evaluate software complexity by variable metric, which measures the number of variables, the distance between two variables and the aggregation of variables.

Based on the defining of independent variables of the state in the equilibrium system, this paper discusses how to select independent variables in different states and the relation between intensive variable and extensive variable when to select independent variables.

The variable metric method for the weakly generalized Lagrange function of nonlinear programming;

In the image reconstruction based on optimization without constraint,the variable metric method,the steepest descent method,and conjugate gradient method were applied to image reconstruction to improve iterative efficiency and reconstructed quality,and their virtue and shortcoming were analyzed.