This study has been conducted in order to determine nutritional value and digestibility and degradability of twigs in four tree species including Zelkova carpinifolia, Gleditchia caspica, Populus deltoids and Quercus castanaefolia through chemical and gas production method using 3 fistulated sheep in National Research Institute for Animal Science, Iran. The experiment conducted based on Randomized Complete Design and obtained data were analyzed by software SAS and Neway. Chemical compounds (crude protein (CP), Neutral Detergent Fiber (NDF), Acid Detergent Fiber (ADF), Ether Extract (EE), Ash, Crude Fiber (CF), NFC (Non Fiber Carbohydrate), Nitrogen Free Extract (NFE) and organic material (OM) and degradation were determined at the times of 0, 2, 4, 6, 8, 12, 24, 48, 72 and 96 h in gas production method and parameters such as (OMD-SCFA-ME-NEL-CP-DMD) were determined. Amount of crude protein for 4 species are as follow: (Z. carpinifolia (11%), G. caspica (15.4%), P. deltoids (10.3%) and Q. castanaefolia (9.5%)), also amount of crude fiber in these trees are respectively 32.7, 18.6, 13.9 and 22.9%. The most and the least fermentation and gas production was observed respectively in G. caspica and Z. carpinifolia. The most mount of gas production belonged to G. caspica with 54 mL/g of dry matter at 96^th h.