Importance analysis is conducted for an off-grid wind power generation system, due to the lack of similar studies particularly on renewable energy systems. Birnbaum importance (BI) and criticality importance (CI) evaluation methods are used to evaluate the importance level of each component and investigate the impact of associated factors. Results reveal that 1) an increase in failure rate of component would cause a corresponding growth of the impact on system reliability, no matter which connection mode is selected; 2) connection mode plays a more important role than failure rate; 3) importance level would be increased with a decrease in the number of identical components connected in parallel; 4) a longer operational time would cause a higher probability of system failure. The implication in this study could drive a transfer of our major concern from the traditional ׳system analysis׳ to the current ׳component analysis׳. This transfer could help to seek more theoretical bases in support of system design, process optimization, probability safety assessment, reliability analysis, etc.