Differential scanning calorimeter and scanning electron microscopy were used to study effect of well-defined functional i-PP-b-PMMA block copolymer in PP/PMMA blends and that of i-PP-b-PS block copolymer in PP/PS blends. The experimental results showed these functional polypropylene copolymers maintained characteristics of high melting point owned by starting isotactic polypropylene polymers, and were clearly proven to be effective compatibilizer in PP/PMMA blends and PP/PS blends. In addition, i-PP-b-PMMA and i-PP-b-PS could increase bending strength and bending modulus of corresponding blending systems.