Switched capacity circuit structures of gradient methods are proposed, the common properties of the steepest descent method, Newton method and quas Newton methods are analysed. Switched capacity circuit structures for unconstrained differential optimization are investigated. 建立了梯度法的开关电容电路结构,分析了最速下降法、牛顿方法和拟牛顿法的共同特点,研究无约束差分优化的开关电容电路结构。