The aim of this study was to evaluate the effect of 35 years of spate irrigation on total biomass (TB) and carbon stock (CS) of dominant species of rangeland plants in Kowsar station located in Gareh Bygone Plain, Fasa, Iran . Samples of Heliantemum lippii, Dendrostellera lessertii and Artemisia sieberi were taken from two sites, irrigated through flood spreading and without flood spreading as the control in autumn 2018. The TB and CS of the plant samples were measured. The obtained data were analyzed using randomized complete block design and the means were compared with Duncan test at P<0.05. The results showed that the effect of spate irrigation, plant species and their interactions on TB and CS was significant at P<0.01. The comparison of the means showed that the reaction of the H. lippii was very high compared to the flood spreading, so that the TB of this species increased from 671.63 to 2013.94 and its CS from 381.90 to 1106.20 Kg/ha, respectively, i.e. 2.00 and 1.90 fold. In the case of D. lessertii, the TB and CS increased 40.00 and 38.64%, respectively. A. sieberi showed a slight negative reaction to flood spreading, so that its TB decreased from 1005.25 in non-flood conditions to 780.9 99 Kg/ha with spate irrigation. The A. sieberi showed a slight negative reaction to flood spreading, so that its TB and CS decreased from 1005.25 and 547.10 in control to 780.99 and 429.30 Kg/ha in flood spreading stripes, respectively. Although, this decreases were not significant at the P<0.05. With respect to the vastness of rangelands in our country, it is possible to store large amounts of carbon dioxide present in the atmosphere (entry the international arena of carbon trade) and reduce the effects of climate change through the flood spreading.