Effect of potassium and magnesium fertilizers on safflower grain yield was studied, using a factorial experiment based on completely randomized block design with three replications at the Agricultural Research Station of University of Mohaghegh Ardabili in 2011. The treatments consisted of potassium fertilizer with three levels (0, 60 and 120 kg ha-1) and magnesium fertilizer (0, 75 and 150 kg ha-1). The results showed that the maximum biomass (8890 kg h-1) was obtained with application of 120 kg K ha-1 and 75 kg ha-1 of magnesium. The highest harvest index (32%) was obtained from with application of 60 kg of potassium fertilizer. The maximum 100 seed weight (5.7 g) was obtained due to the application of the 60 kg potassium plus 75 kg ha-1 of magnesium. Application of 120 kg ha-1 potassium and 150 kg magnesium produced the greatest grain yield (2447.1 kg ha-1). The highest seed oil content was obtained by the application of 60 kg ha-1 potassium. The highest oil yield obtained with application of 120 kg potassium (790 kg ha-1) and 150 kg magnesium (700 kg ha-1) though, it was not significantly different with the oil yield at the presence of 60 and 75 kg ha-1 of potassium and magnesium, respectively. Thus, application of 60 kg ha-1 of potassium and 75 kg ha-1 of magnesium due to lower production costs deems appropriate for safflower production in Ardabil.