Since most of the available component-based software reliability models consume high computational cost and suffer from the evaluating complexity for the software system with complex structures,a component-based back-propagation reliability model(CBPRM)with low complexity for the complex software system reliability evaluation is presented in this paper.The proposed model is based on the artificial neural networks and the component reliability sensitivity analyses.These analyses are performed dynamically and assigned to the neurons to optimize the reliability evaluation.CBPRM has a linear increasing complexity and outperforms the state-based and the path-based reliability models.Another advantage of CBPRM over others is its robustness.CBPRM depends on the component reliabilities and the correlative sensitivities,which are independent from the software system structure.Based on the theory analysis and experiment results,it shows that the complexity of CBPRM is evidently lower than the contrast models and the reliability evaluating accuracy is acceptable when the software system structure is complex. Since most of the available component-based software reliability models consume high computational cost and suffer from the evaluating complexity for the software system with complex structures, a component-based back-propagation reliability model (CBPRM) with low complexity for the complex software system reliability evaluation is presented in this paper.The proposed model is based on the artificial neural networks and the component reliability sensitivity analyzes. These analyzes are performed dynamically and assigned to the neurons to optimize the reliability evaluation. CBPRM has a linear increasing complexity and outperforms the state. -based and the path-based reliability models. Another advantage of CBPRM over others is its robustness. CBRM depends on the component reliabilities and the correlative sensitivities, which are independent from the software system structure. Based on the theory analysis and experiment results, it shows that the complexity of CBPRM is evidently lower than the co ntrast models and the reliability evaluating accuracy is acceptable when the software system structure is complex.