The carcass was found during routine patrolling by forest guards and it is assumed that the animal died a natural death, Park sources said.
However, the park authorities have sent samples of the rhino for testing to check whether it was poisoned.
The carcass was found near Kuthori Lower Primary School, which is behind Burpahar Range in Nagaon district, KNP sources said.
On October two, the body of a rhino, also suspected to have died a natural death, was recovered near Daflang camp in Bagori Range of the KNP.
The total number of rhino deaths so far this year in this 430 sq km UNESCO world heritage site is 35.
Assam is home to two-third of the world's one-horned rhinos and Kaziranga is the home-land of over 2,000 of them.