Abstract: Objective A new combined LS(CLS)method is proposed which considers the random error in a designmatrix after a brief introduction of TLS and its iteration algorithm and the SVD algorithm.The newalgorithm can be applied for TLS parameter estimation,so that TLS can be integrated with classicalLS in theory.By proposing rigorous accuracy assessment formulas for TLS under the new algorithm,this paper solves the bottleneck problem which restricts the application of TLS,and then shows thefeasibility and correctness of the new method through examples.The research results are meaningfulnot only for TLS theory,but also for the whole data processing theory.