The present invention relates to a process for the preparation of Azilsartan Medoxomil Potassium. The invention further relates to novel highly crystalline polymorph of Azilsartan Medoxomil Potassium and composition comprising it. The invention provides thermostable highly crystalline polymorph of Azilsartan Medoxomil Potassium and process to produce a composition comprising the novel highly crystalline polymorph of Azilsartan Medoxomil Potassium.