This study shows the operational availability(Ao) analysis of the supply chain with maintenance functions using the system dynamics simulation. The simulation uses 60 equipments which are serial systems composed by 4 major components. And every entities are connected each other by causal loops. So whole simulation executed like one organic system. Specially we consider 2 constraints, one is the number of spare parts and the other is maintenance capacity level. 2 constraints have 11 levels each so the simulation has 121(11*11) scenarios which scenario has 30 different random number seed. The simulation executed total 3,630(11*11*30) times. We analysis average Ao of total equipments by 121 scenarios and additionally the regression of the average Ao and 2 constraints. As the result, we can get the more accurate values by the system dynamics simulation than the regression to analysis complex system like the supply chain with maintenance functions.