Understanding the structure and nature of genotype environment interaction (GEI) is important in plant breeding programs. In order to study GEI effects on the seed yield and identify stable genotypes, 12 winter rapeseed (Brassica napus L.) promising lines along with Okapi cultivar (control) were evaluated in six cold (Bojnurd, Hamedan and Arak) and temperate regions (Karaj, Kermanshah and Isfahan) in 2010-2011 and 2011-2012 cropping seasons by using a randomized complete block design with three replications. Combined analysis of variance performed by assuming years and locations as random and genotypes as fixed factors. The results of combined analysis of variance showed that the year × location × genotype was significant at 5% level of probability. The GEI was examined using multivariate analysis technique as principal coordinate analysis (PCOA). According to grand means of test environments and total mean yield, test environments are grouped to low (three environments) and high (five environments) mean yield. Considering plot of minimum spanning tree and values of centroid distances, line G5 (L63) and Okapi cultivar were identified for unfavorable or poor environmental conditions. Also lines G3 (L201) and G8 (L119) were identified for favorable environments.