Abstract: Combining ability of inbred lines is important information in maize(Zea mays.L) hybrid breeding programs to incorporate genotypes from various germplasm sources. This study was conducted with germplasm developed using double haploid technology (DH) lines. Sixty-six F1 crosses resulted from diallel crosses of 12 maize inbred lines with four standard checksArgane (AMH800), Kolba (AMH853), Jibat (AMH851) and Wenchi (AMH850) were evaluated based on partial diallel meeting fashion and its relative analysis to estimate general combining ability (GCA) and specific combining ability (SCA) for yield and yield related traits using alpha-lattice design with three replications during the 2017 cropping season at Ambo, Holeta and Kulumsa Agricultural research center of Ethiopian Institution of agricultural Reseach Institution. Analysis of variance showed that mean squares due to entries were significant for most of the traits studied, such as grain yield, thousand kennels weight, days to silking, ear per plant, plant height, ear height, husk cover, ear rot, ear aspect, plant aspect, kernel rows per row, ear length and ear diameter .Genotypes x environment interactions showed highly significant difference at (p<0.01) for most traits but significant (p<0.05) for grain yield.Mean squares due to crosses were significant (p<0.05) at two locations (Holeta and Kulumsa). Alleles at a locus can have an effect on the trait by themselves but can also affect the phenotype through interactions with other alleles the so called non- additive effect, while when allele of a single gene (in heterozagote )combine so that their combined effects equal the sum of their individual effects called additive gene action. GCA and SCA mean squares revealed significant (p<0.05) differences for grain yield and most yield related traits in all location and across location. Inbred lines P2, P9 and P12 were good general combiners as these lines showed significant and positive..................