The present invention relates to a process for preparing ultra-high molecular weight polyalphaolefin. The process consists of polymerizing alphaolefin monomers using the catalyst system consisting of supported Ziegler-Natta catalyst without internal donor in presence of co-catalyst based on alkyl aluminums. The resulting ultra-high molecular weight polyalphaolefins having intrinsic viscosity ≥10 dL/g are used as drag reducing polymers for increasing throughput in the pipelines by reducing frictional resistance in turbulent flow.