In order to study the effect of sowing date on grain yield and grain-filling duration of triticale cultivars, an experiment was conducted based on strip-plot experiment with four replicates at Ramin Agricultural Research and Educational Center (RAREC) during 2009-10. The sowing date treatments were November, 10th (Aban, 20th) and December, 4th (Azar, 14th) and the cultivars include: ET.79-3،ET.79-4،ET.79-17،ET.82-8،ET.82-15،ET.82-1،ET.83-20،ET.84-5،ET.84-8،ET.84-15،ET.85-7، ET.85-9, and Govanilo -91. Results showed that the sowing date had significant effect on the duration from planting to tillering, the duration from planting to spiking, and the amount of chlorophyll. There were significant differences between the cultivars for plant height, spike height, the duration from planting to spiking, and the amount of chlorophyll. The first sowing date with 34.13-day duration of grain-filling had lower filling rate in comparison to the second sowing date. In the second planting date, due to more heat, the during of grain-filling period was reduced to 25.5 days. Nevertheless, as a result of the proper temperature at the region, grain-filling rate increased to 1.51 mg/day. Therefore, in order to increase the grain-yield and 1000 –seed-weight, one possible way is to use the cultivars which, along with the heat-stress tolerance, are capable of increasing the duration of grain-filling through increasing their photosynthesis. As a result, ET.79-3, ET.82-16, and Javanilo-92 cultivars in late-sowing time (Dec, 4th) and ET.84-5 and ET.79-17 in early-sowing (Nov, 10th) showed to have maximum grain yield.