The invention discloses a 
nitrogen-doped 
porous carbon-coated 
metal nano composite catalyst and a preparation method thereof. The preparation method comprises the following steps: (1) adding a 
fluoride into an acidic solution for reaction, then adding M<n+1>AX<n>, carrying out magnetic stirring reaction under a water bath condition, cleaning a product with deionized water, centrifuging, then sequentially carrying out ultrasonic cleaning and centrifuging with an 
organic solvent and deionized water, and carrying out 
freeze drying so as to obtain a reactant 1; 2) weighing a certain amount of thereactant 1, adding deionized water and an 
organic solvent, carrying out uniform 
ultrasonic dispersion, dissolving a 
transition metal salt and 
urea in deionized water, adding an obtained mixture in anobtained 
mixed solution of the reactant 1, and carrying out magnetic stirring reaction under an 
oil bath condition to obtain a reactant 2; 3) performing heat treatment on the reactant 2 and a 
nitrogen-containing compound in a high-temperature furnace to obtain a reactant 3; and 4) performing high-temperature reduction on the reactant 3 in a protective 
atmosphere to obtain the 
nitrogen-doped porouscarbon-coated 
metal nano composite catalyst. According to the preparation method, the problems that the 
oxygen reduction catalyst prepared in the prior art is easy to 
agglomerate and the ORR activityis reduced due to less 
exposure of active sites are solved.