Purple soil is an important type of soil resource, occupying an important position in agricultural production in China. The soil column leaching method was used in this experiment to explore effects of nitrogen fertilizer on purple soil surface electrochemical properties relative to type of the fertilizer and on nitrogen balance in the soil-crop system. Results show that compared with the original soil, purple soils in all fertilization treatments increased in surface charge by 0.05 ~ 0.7 cmol kg^-1; the treatments low in nitrogen level (100 and 200 mg kg^-1) displayed an order of Treatments U (Urea) > Treatments AS (ammonium sulfate) > Treatments AN (ammonium nitrate) in , surface charge; while the treatments high in nitrogen level (300 and 400 mg kg^-1) did a different order of Treatments AS > Treatments U > Treatments AN; purple soils in all the treatments increased in specific surface area, particularly in Treatment N1 (100 mg kg^-1 urea) being 78.04% higher than in CK; the effect of urea was much higher than the other two; Treatment L4 (400 mg kg^-1 ammonium sulfate) was the lowest in the effect, being only 0.06% higher; among the treatments the same in N level, Treatment AS was the highest in both surface charge density and electric field strength, while Treatment U the lowest; the effect was apparently higher in treatments low in N level than in treatments high in N level. Obviously, N fertilizers, different in type and application rate, varied in type and concentration of electrolyte, thus leading to change in soil pH and eventually in soil electrochemical properties and hence in soil nutrient holding capacity and nutrient availability. In this experiment, the non-electrolyte system, when low in concentration, can significantly affect the surface electrochemical properties of purple soil, but the effect is obvious only when strong electrolyte is high in concentration.