The cyclic voltammetric behavior of uranyl ion was investigated at hanging mercury drop electrode in perchlorate supporting electrolyte.  The standard heterogeneous electrons transfer rate constant “ks” for the reduction of uranium from U(VI) to U(V) state was 2.72 x 10-3 cm sec-1 in simple perchlorate medium and in the presence of 0.40 mol L-1 sulphate ions the value of ks was 2.56 x 10-3 cm sec-1. The effect of temperature on the values of ks was investigated and different thermodynamic constants,  H*,  S* and  G298*, were calculated. The values of   H*,  S* and  G298* were 7.97 kJ mol-1, -23.80 J mol-1 K-1 and 15.06 kJ mol-1 in simple perchlorate medium and 3.99 kJ mol-1, -37.70 J mol-1 K-1, and 15.22 kJ mol-1 in sulphate medium. The stability constants of uranyl sulphate complexes were calculated from the analysis of shift in peak potential of uranyl ions with increasing concentration of sulphate ions. The values of logß1 and logß2 for 1: 1 and 1: 2 uranyl sulphate complexes were found to be 1.90 ? 0.01 and 2.92 ? 0.02 respectively, which are in close agreement with the literature values.