Polypropylene random copolymer (PP-R), as a material for pipe applications, has a unique molecular structure resulted from copolymerization of propylene with ethylene comononmer. The performance of PP-R,including their processability and final mechanical properties, can be simultaneously improved by finely controlling the molecular weight distribution (MWD). In this study, two representative samples were chosen from a material optimization design procedure, one of which has more content of ultra high molecular weight component. The chain structures, rheological properties, crystallization behaviors and mechanical properties of the two samples were analyzed. Results from rheology tests showed that broadening MWD will improve the processability of the materials. The samples were then fractionated according to molecular weight and subsequently studied by isothermal and non-isothermal crystallization kinetics as well as self-nucleation and annealing (SSA) technique. The results indicated that the ultra high molar mass component resulting from a broader MWD can act as nucleation agent, which might decrease the spherulite size and on the other hand increase the tie-chain content of PP-R. Finally, polarized optical microscope (POM) and tensile tests were carried out to extensively ascertain these speculations. It appears that finely controlling the MWD has a synergetic effect on the processability and the final mechanical properties of PP-R.