Orchard grass (Dactylis glomerata L.) and smooth bromegrass ( Bromus interims L.) are of the most important Perennial pasture plants in Iran that are capable of cultivation, as well as mixtures with legumes has to be pure. This study was to estimate genetic diversity between and within communities through evaluation of two species of grass in the Orchard grass and smooth bromegrass, general combining abilities of traits associated with yield and forage quality in order to identify genotypes suitable for qualitative and quantitative characteristics important for production of synthetic varieties, estimate genetic parameters of additive gene effects, and heritability for different traits were private. The results of this study showed that in all measured traits in both years, there is considerable variation. Most phenotypic variation coefficients bromus, in the first year of the collar diameter and dry forage yield, in the second year was related to height and panicle length. Most genetic diversity in the first year was dedicated to the collar diameter and dry forage yield. Analysis of variance, the effect for the traits days to flowering, days to anthesis, height, collar diameter and number of stems showed significant. Smooth bromegrass families studied in terms of all traits were significant at 1% probability level. Comparison of performance three cut showed smoth bromegrass family (4) with performance (27/14) in both years the family has been leading in the production of dry forage yield. Orchard grass family of 4 in the first year and the three cut was the highest dry forage yield, but in the second year, family (18) in all three of cut was won the highest performance. Families (5), (6) and (23) of smooth bromegrass had the highest general combining abilities (71/6) in the days to heading and days to pollination. Family (4) in both years had the highest amount of dry forage yield. Most general combining abilities in the Orchard grass belonged to families (20) and (13). in 89 years families (4) and 90 years (18)had the highest general combining ability for dry forage yield. Phenological traits in smoth bromegrass showed high heritability. Results from parent offspring regression in most traits were consistent with the results of the progeny. Heritability of yield in smooth bromegrass based on one year (46 percent), based on two years (49) and to the parent - offspring (24) was obtained. Correlation between days to flowering with days to pollen traits, flag leaf length, panicle length, spring growth, persistency and dry matter percentage was significant. Positive genetic correlation between days to heading and days to pollination was found in both plants. Significant correlation between height and number of stems and dry forage yield was observed. Based on cluster analysis, Euclidean distance of 1.5, bromus families were in the three groups. Analysis of variance showed a significant group in the groups mean squares for plant height, stem number, percentage of dry matter and dry forage yield. Orchard grass genotypes based on cluster analysis, Euclidean distance of (22), were divided into two groups. Key words : smooth bromegrass, orchard grass, synthetic varieties, genetic variability, general combining ability