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A field study was conducted at a private farm in AL-Anbar Governorate city of Ramadi- the village of Albu Shaban, during the successive spring and autumn seasons (2020). Five pure lines of maize (Zea mays L.) (ART-B-17, Zm-1, SYn-33, Inb-27, Zm-5 ) were crossed in all possible combinations including reciprocal, during the spring season of 2020 to produce 20 diallel and reciprocal crosses. planted single cross and parents in autumn seasons by using Randomized Complete Block Design (R.C.B.D), with three replications to determine the best pure lines and their single crosses, depending on its performance, genetic analysis for General and Specific Combining Ability (GCA; SCA), Gene Action, and Heritability, using the approach of Griffing method 1 with the fixed model for traits: days to 50% silking, plant height, number of ears per plant (NEPP), number of grains per row, 300-grain weight, and grains yield per plant. The results of indicated that there were highly significant differences for all the studied traits. Where parent line (5) gave the highest mean for most of the studied traits, including Grains Yield per plant 156.73 gm. Regarding the crosses, the diallel cross (1×5) gave the highest mean Grains Yield per plant reach 231.15 gm, while in reciprocal crosses, the cross (4×1) gave the highest mean Grains Yield per plant reached 186.35 gm. The results show that the estimation of the reciprocal effect was significant in most of the reciprocal crosses. The results of the genetic analysis showed that there were high significant differences in MSgca, MSsca, and MSrca for all studied traits except for the mean squares of days to 50% silking trait. The parent line (5) showed the best effect of the general combining ability in Grains Yield per plant traits reached 13,691, and the number of grains per row was 1,280 and 300 Grain Weight reached 2,326, while the cross (1×2) and reciprocal cross (5×4) showed the best effect of Specific Combining Ability of Grains Yield per plant traits was 15,285 and 15,718, respectively. The ratio of σ2sca\σ2gca and σ2rca\σ2gca was less than one for all the studied traits in the diallel and reciprocal hybrids. This was reflected in the value of the mean value of the degree of dominance that was greater than one in all the studied traits of the diallel and reciprocal crosses. The ratio of broad-sense heritability was high and in the narrow sense low in most traits studied in the diallel and reciprocal crosses.