With the urban soil of Tangshan City as the study target, the authors evaluated the environmental quality of soil heavy metals and pollution characteristics by adopting the single factor index method and Nemerow comprehensive index method. Besides, the potential ecological hazard index suggested by Hakanson was used to assess the ecological hazards of heavy metals in urban soil. All of the heavy metal elements are not in the pollution state, especially all of Hg, Ni, Cr and As are in a clean condition. Considering synthetically the potential ecological hazards of heavy metals, the authors have found that the percentage of small, medium, high and strong ecological hazard is respectively 73.02%, 26.98%, 0% and 0%.Therefore, the general performance is the small potential ecological hazard.