It is likely that the demand for multiprocessor system-on-chip (MPSoC) with low power consumption and high reliability in the presence of soft errors will continue to increase. However, low power and reliable MPSoC design is challenging due to conflicting trade-off between power minimisation and reliability objectives. This thesis is concerned with the development and validation of techniques to facilitate effective design of low power and reliable MPSoCs. Special emphasis is placed upon system-level design techniques for MPSoCs with voltage scaling enabled processors highlighting the trade-offs between performance, power consumption and reliability.An important aspect in the system-level design is to validate reliability in the presence of soft errors through simulation technique. The first part of the thesis addresses the development of a SystemC fault injection simulator based on a novel fault injection technique. Using MPEG-2 decoder and other examples, it is shown that the simulator benefits from minimum design intrusion and high fault representation. The simulator is used throughout the thesis to facilitate the study of reliability of MPSoC.On-chip communication architecture plays a vital role in determining the performance and reliability of MPSoCs. The second part of the thesis focuses on comparative study between two types of on-chip communication architectures: network-on-chip (NoC) and advanced microprocessor bus architecture (AMBA). The comparisons are carried out using real application traffic based on MPEG-2 video decoder demonstrating the trade-off between performance and reliability.The third part of the thesis concentrates on low power and reliable system-level design techniques. Two new techniques are presented, which are capable of generating optimised designs in terms of low power consumption and reliability. The first technique demonstrates a power minimisation technique through appropriate voltage scaling of the MPSoC cores, such that real-time constraints are met and reliability is maintained at acceptable-level. The second technique deals with joint optimisation of power minimisation and reliability improvement for time-constrained MPSoCs. Extensive experiments are conducted for these two new techniques using different applications, including MPEG-2 video decoder. It is shown that the proposed techniques give significant power reduction and reliability improvement compared to existing techniques