The electrocatalytic behaviour of highly dispersed Pd/carbon catalyst prepared by ion preadsorption method for oxygen reduction in alkaline solution was investigated with soft-embedded rotating disk electrode and soft-embedded microelectrode method. The results showed that this catalyst has high catalytic activity both for oxygen and for HO2- reduction in alkaline solution. The occurrence of the peak current on the polarization curves of oxygen reduction on the catalyst when potential was scanned negatively, and the occurrence of the negative slope of IDN/I-R vs. omega(-1/2) relation were analyzed. It is proved that the competition of Pd and support surface for oxygen molecules during oxygen reduction was the main cause for this new phenomenon.