Based on wholesystem dynamic error modeling method and theory, the theory and method of dynamic accuracy loss decomposition and tracing were studied. Using bill belt signal reconstruction improvement arithmetic, the accuracy loss signal of emulation system was decomposed, its frequency components of the system’s main insider structural units was obtained. Then by using non-linear mapping ability from input to output of BP NN, model parameters of the built accuracy loss function model of each insider cells were estimated, and the signals decomposing were achieved. Using the error characteristic of each insider structural units and the systemic whole error model, the signals tracing were achieved. Experimental result indicated that by using BBSRIA (bill belt signal reconstruction improvement arithmetic), reliably decompose and tracing of the accuracy loss signal could be achieved. 