Rational engineering of simple, economical and durable nonprecious metal electrocatalyst with excellent oxygen reduction reaction (ORR) activity is crucial for the electrochemical energy conversion devices, such as metal-air batteries and fuel cells. Here, we developed a highly efficient ORR electrocatalyst with rich and well-dispersed Fe-Nx active sites and iron nanocrystals decorated three dimension (3D) porous carbonaceous matrix by a rational designed carbonaceous spheres templated strategy. The fabricated electrocatalyst exhibits outstanding ORR activity with onset potential of 1.0 V and half-wave potential of 0.90 V versus reversible hydrogen electrode in alkaline media, which is much better than benchmark Pt/C. In addition, it presents particularly better performance in terms of superior stability and excellent methanol tolerance capacity. Experimental studies display that the remarkable ORR activity primarily originates from the synergetic effect of rich Fe-Nx active sites, sufficient carbon encapsulated metallic iron nanocrystals and desired meso/microporous structure. What worth to point out is that the facile synthetic technique can be extended to fabricate other low cost highly active transition metal-N-carbon scaffolds ORR electrocatalysts.