Abstract
The paper tries to investigate and compare three production control policies, HP production control policy, zero production control policy and (z, Z) production control policy, in flow-shop manufacturing system,A HP production control policy is characterized by a number z*, which is regarded as the optimal amount of inventory to be kept. If current inventory level exceeds z*, the system be set to produce nothing；if less than z*, the system should be set to produce at the maximum rate；if the inventory level exactly equals z*, the system should be set to produce exactly enough to meet demand and thereby keep the inventory level at z*. A zero production control policy is also characterized by a number z* which is regarded equal zero.The simulation to estimate the expected inventory & shortage per unit time and to estimate the (z, Z) values for (z, Z) production control policy and the Z* value for HP production control policy which are based on that we model the unreliable single machine system in a renewal process.