Abstract: Considering the mix-up of the definition of machine safety and machine safety-capability, the differences among machine safety, machine safety-capability and reliability are discussed. Then the advantages and disadvantages of present qualitative, quantitative and other methods for machine safety-capability assessment are analyzed. It is concluded that the qualitative assessment methods for machine safety-capability have a high subjectivity, and quantitative assessment methods can not solve component's multi-state, non-monotonic and common cause failure problems, meanwhile, the calculation of criticality degree of components is complicated and is difficult for engineers to apply directly. Finally, design plans for machine safety-capability qualitative and quantitative assessment model are provided to settle those problems.