Based on USEPA framework of health risk assessment, the multi-pathway health risk assessment model was developed for heavy metals in the case soils. Monte-Carlo simulation was adopted to quantitatively study the effect degree of parameter uncertainty on assessment result, and sensitive parameters were further identified by sensitivity analysis. The results without Monte-Carlo simulation showed that there was no non-carcinogenic risk because of 1＞HICd＞HINi while it was under carcinogenic risk due to RCd＞1.0×10-6. However, with the Monte-Carlo simulation of selected variables, it indicated that the parameter uncertainty made the non-carcinogenic risk assessment results varying within 0.1~0.2, and the carcinogenic risk assessment results varying in the range within 1 order of magnitudes. Therefore, the parameter uncertainty made the value range of RCd span 1.0×10-6 and it was probable to mislead the corresponding decision-making. Sensitivity analysis indicated that the contents of Cd in case soils and vegetables, and the weight for the target receptor should be treated as sensitive variables, which were the main source of parameter uncertainty. To further improve the credibility of assessment with cost-benefit consideration, data of the sensitive variables should be preferentially gathered.