Preeclampsia or high blood pressure in pregnancy is one of the special disorders during pregnancy. It seems that oxidative stress plays an important role in the occurrence of this disease. The purpose of this study is to investigate the relationship between the A313G polymorphism in exon five of the glutathione S-transferase gene (GSTP1) and the risk of preeclampsia in a case-control study. In this study, blood samples were collected from 70 healthy pregnant women and 70 women with preeclampsia. After genomic DNA extraction, the PCR-RFLP method was performed to check the genotype in GSTP1-A313G and the genotypic frequencies of AA, AG, and GG were determined in all samples. Also, using bioinformatics software, the effect of the above polymorphism on the protein structure was investigated. Statistical analysis for A313G polymorphism showed that AG (OR: 1.1684, 95% CI: 0.5877-2.3228, p=0.657) and GG (OR: 1.3793, 95% CI: 0.3376-5.6359, p=0.654) genotypes were not associated with risk of preeclampsia in the population of northern Iran. However, bioinformatic analyzes have shown that this polymorphism does have a destructive effect on the protein structure. However, more studies with larger sample sizes are needed to draw firm conclusions.