Length composition data (fork length) of kawakawa (Euthynnus affinis ), landed between April 2003 to March 2005 in Coastal Waters of Hormozgan province in Iran ( Persian Gulf and Sea of Oman) , were monthly used to estimate the p opulation parameters and for the assessment of the stock. The growth parameters of von Bertalanffy equation were estimated as L_∞: 87.66 cm, K: 0.51 per year and t₀: -0.23 year. The estimated value of total mortality, natural mortality and fishing mortality were Z: 2.37, M: 0.65, F: 1.72 per year, respectively. Exploitation ratio (E) and Exploitation rate (U) were estimated as 0.72 and 0.65. The Annual total stock at beginning of year was calculated to be 7924 t and Annual average standing stock (S) was equal to 2994 t. By using analyses knife-edge selection method, biological reference points for kawakawa stock was calculated as, Y'/R (relative yield per recruitment) =0.062, B'/R (relative biomass per recruitment) =0.13, F max (Fishing mortality at maximum sustainable yield) =1.6, E max (Exploitation ratio at maximum sustainable yield) = 0.68 Fopt (Precautionary average target ) =0.33 year^-1 and Flimit=0.43 year^-1. As the exploitation ratio of kawakawa stock in this study was calculated to be over 0.5, it strongly recommended minimizing the fishing activity in this area.