Modified natural rubber masterbatch and method for producing the same as well as rubber composition and tire

This invention provides a method for producing a modified natural rubber masterbatch, which comprises the step of mixing a modified natural rubber latex, which is formed by adding a polar group-containing monomer to a natural rubber latex to graft-polymerize the polar group-containing monomer onto a natural rubber molecule in the natural rubber latex, with a slurry solution formed by previously dispersing a filler into water, and a modified natural rubber masterbatch produced by the method and capable of highly improving a low loss factor, a wear resistance and fracture characteristics of a rubber composition.