For analog circuits, relative accuracy is important in controlling the performance of the circuit, verifying the influence of relative accuracy is desired in simulations. Since the CPU time of relative accuracy analysis is very long, in many cases simulation is performed in small sized circuits. We propose a relative accuracy simulation method, which was difficult in FAST SPICE, using ADiT™. The proposed method reduces the simulation time to use the FAST SPICE ADiT™. Also, we propose a method using CPU distribution and explain the experimental results.