A field experiment was carried out in the fields of the Department of Field Crops/ College Agriculture - University of Anbar (Abu Ghraib) during the spring and autumn seasons of 2017. The aim of this study was to deterimnie the effect of conservation agriculture at three tillage systems (no-tillage (T1), surface tillage (T2) and conventional tillage (T3)) and three plant densities )66666 (D1), 57143 (D2) and 50000 (D3)( in plant growth and yield of two composit varieties  of maize (Maha (V1) and Fajr 1 (V2)). Split-split plots were used according to the randomized Complete Block Design (RCBD) with three replicates. The results were summarized as follows: No-tillage system (T1) was superior of the surface tillage and conventional tillage (T2 and T3) in weight of 300 grains for spring and autumn seasons. And the same tillage system superior in autumn seasons in plant height, No. of ears per plant and grain yield (6.92 ton ha^-1). The increasing plant density significantly increased leaf area, weight of the grain and grain yield, which reached 4.97 ton ha^-1. The high density of the plant was (D1), and the medium plant density (D2) were higher in some traits such as plant height for spring and autumn seasons .The cultivar Maha (V1) was superior than the Fajr 1 cultivar (V2) in some traits, including plant height, flage leaf area and weight of the grain, grain yield (6.70 ton ha^-1). The effect of interaction between the tillage systems and the plant density was significantly differed in several traits, where (D2 × T1), produced the highest average of the plant charcters for the autumn season. While the combination (D3 × T1) gave the highest mean of No. of ears per plant (1.740) and the highest average weight of 300 grain reached 59.68 and 62.52 g for the spring and autumn seasons, respectively. The combination (V2 × T1) recorded the highest mean plant height, weight of 300 grains. The combination (V1 × D1) has the highest weight of 300 grains, and grain yield (9.85 ton ha^-1)for the autumn season. (T1 × D3 × V2) gave the highest weight of 300 grains (60.33 g) for the spring season.