The invention discloses an electricity reliability index rapid calculation method based on caching data multithread processing, solving the problem that the electricity reliability index analytical calculation efficiency is too low. The method comprises the steps of creating a data cache region in a memory, and creating data blocks by taking administrative units, equipment register dates or power failure occurrence dates as main keys by dividing according to business types; establishing a change cache region in each data block, recording data change, and merging the data of the change cache region and basic data in regular time; evenly distributing data relating to the index calculation to a plurality of threads to carry out basic index calculation, merging the basic index calculation result of each thread, and calculating the reliability comprehensive index of each level of management unit. According to the method, multiple data blocks are used for caching business data, technical measures such as the data change cache regions and the multithread processing are adopted, the basic data retrieval and calculation efficiencies of the electricity reliability business are improved, and the rapid calculation of the electricity reliability index is realized.