系统分析，旨在研究特定系统结构中各部分（各子系统）的相互作用，系统的对外置口与界面，以及该系统整体的行为、功能和局限，从而为系统未来的变迁与有关决策提供参考和依据。系统分析的经常目标之一，在于改善决策过程及系统性能，以期达到系统的整体最优。

系统分析被看作是系统工程的一个重要进程和核心组成部分，以及系统理论的一项应用。 在系统开发生命周期中，系统分析阶段先于系统设计，是系统开发前期不可或缺的工作。 系统分析大量借用数学模型、数学分析、计算机模拟等定量分析方法，试图在具有不确定约束或边界条件的情况下，对系统要素进行综合分析、描述，得出较为准确或合理的结论。

The Merriam-Webster dictionary defines systems analysis as "the process of studying a procedure or business in order to identify its goals and purposes and create systems and procedures that will achieve them in an efficient way". Another view sees systems analysis as a problem-solving technique that decomposes a system into its component pieces for the purpose of the studying how well those component parts work and interact to accomplish their purpose. Analysis and synthesis, as scientific methods, always go hand in hand; they complement one another. Every synthesis builds upon the results of a preceding analysis, and every analysis requires a subsequent synthesis in order to verify and correct its results.