The invention discloses a three-dimensional dynamic grinding force detection device and its decoupling algorithm, which mainly solves the problems of low natural frequency, narrow measurable dynamic force range and piezoelectric grinding force measurement of the existing resistance strain grinding force measuring instrument. The instrument is complicated to manufacture, expensive, unable to detect static force, the multiple linear regression decoupling algorithm is highly dependent on the linearity of the detection device, and the decoupling effect is unstable. The three-dimensional dynamic grinding force detection device is mainly composed of a base, a column, a support, an elastic thin plate group, an upper cover plate and a resistance strain gauge group. The workpiece to be processed is installed on the upper surface platform through threaded connection. During grinding, the grinding force acts on the workpiece and is transmitted to the column through the upper surface platform, causing the column to deform accordingly, and then transmitted to the three sets of elastics installed in parallel with it. Thin plates, three groups of elastic thin plates are installed in two pairs vertically, causing the three groups of resistance strain gauges pasted on the elastic thin plates to produce corresponding resistance value changes, and after signal conditioning and collection, they are transmitted to the PC, realizing Three-dimensional dynamic grinding force detection. The decoupling algorithm uses the BP neural network as the decoupling model, and optimizes its initial weight and threshold parameters through the genetic algorithm to obtain the optimal decoupling model and realize the high-precision decoupling of the three-dimensional grinding force signal. The invention has ingenious structural design, high natural frequency, wide range of measurable dynamic force, and can measure static force at the same time, with low inter-directional coupling and simple manufacture, which greatly reduces the manufacturing difficulty and production cost of the three-dimensional dynamic grinding force detection device, and at the same time The decoupling algorithm has fast convergence, high precision and high reliability, and has good practical and popularization value.