Background: Despite overall improved outcomes in Wilms' Tumor (WT), certain populations of patients continue to experience poor survival and increased rates of relapse. This article is dealing with studying the prognostic value of genetic marker and test its association with the risk of WT relapse. The measurements of b-FGF were made by RT-PCR and Immunohistochemical analysis. Methods: To study the discrepancy between patients with WT relapse and WT relapse-free, a prospective trial was carried out for 40 children; 20 patients had disease relapse and 20 remained relapse-free at last follow-up. Twenty patients' autologous normal renal tissue was used as control. Formalin-fixed, paraffin-embedded blocks of tumors and healthy renal tissue were used to obtain the total RNA. The expression of the b-FGF gene was assessed using quantitative real-time PCR (qRT-PCR) and normalized to glyceraldehyde 3-phosphate dehydrogenase (GAPDH) as an endogenous control.  Results: The comparison between WT relapse and relapse-free, the b-FGF had significant difference (P value < 0.05) and strong FGFR3 expression was detected in the cytoplasm of tubules in relapsed patients 14(60.87)% compared to free relapsed patients 3(10.71)%. Conclusions: WT with the higher expression levels of b-FGF are associated with an increased risk of relapse disease which can serve as future prognostic predictors and help to support patients for treatment and follow-up regimen.