In order to accommodate the production lines to the customer and market requirements, flexible manufacturing has always been considered by researchers in various industries. One of the efficient flexible manufacturing environments is flexible job-shop problem (FJSP), which is an extended derivation of classical job-shop scheduling problem to meet the requirements of modern job-shop.  Since in the literature of flexible job shop scheduling problem (FJSP), FJSP is known as an NP-hard problem, two optimization techniques including harmony search (HS) algorithm and firefly algorithm (FA) are adopted for FJSP. At the end, by implementing well-known problems of FJSP, we will study the performance of the proposed algorithms