The research was conducted at the Forestry Nursery of the Directorate of Agriculture in Deir Ezzor Governorate during the growing season of 2019. The objective of the study was to study the effect of humic acid application and different irrigation intervals on chemical composition of blue panic plant (Panicum antidotale). The experiment was implemented in a Randomized Complete Block Design (RCBD) by planting Panicum seeds in polyethylene bags filled with 2 soils to 1 sand mixture in four replicates. Whereas three irrigation intervals (7, 14, and 21 days) and two humic acid application treatments (control without addition and application of humic acid) were used. Fresh plant sample from each treatment was taken at each cut, and samples were dried at 70C until weight was stable. Chmeical compostion was conducted for the samples and dry matter %, crude protein %, crude fiber %, total carbohydrate %, and ether extract % were estimated according the the common methods. The results showed that the control treatment (irrigation every 7 days) was significantly superior to the two irrigation treatments every 14 days and 21 days in the percentage of soliable carbohydrates (42.09%). While, irrigation treatment every 14 days outperformed the other irrigation treatments and recorded the highest values of percentage of crude protein (17.07%) and the percentage of ether extract (2.73%). The irrigation treatment every 21 days gave the highest values of ash percentage (16.38%). No significant differences were recorded between the irrigation treatments for the percentage of dry matter and the percentage of crude fiber. The control treatment of humic acid outperformed the addition of humic acid interms of the percentage of crude fiber (CF), while the treatment of addition of humic acid outperformed the control in the percentages of crude protein (CP), ash and ether extract (EE). No significant differences were recorded between the application and control of humic acid treatments in dry matter % and the percentage of soluble carbohydrates. The effect of the interaction between irrigation intervals and the application of humic acid was significant for all the studied characteristics. The control treatment (irrigation every 7 days) with the addition of humic acid recorded the highest values for the percentage of soluble carbohydrates (42.92%). The irrigation treatment every 14 days with the addition of humic acid gave the highest values in the percentage of crude protein (17.81%), the percentage of ash (16.55%) and the percentage of extracted ether (2.81%). As for the irrigation treatment every 21 days with the addition of humic acid, had the highest values for the percentage of dry matter (96.25%)