A novel scheme that combines the cross-polarization (CP) with a single-pulse (SP) experiment is developed to quantitatively analyze compositions of multiphase polymers with marked difference in phase mobility. The CPSP method is able to record both CP and SP spectra in one experiment and avoid excessive lone relaxation delay, saving considerable experimental time. The quantification of CP spectrum is done by measuring the enhancement factor of CP with a reciprocity relation, while the quantification of SP is derived directly from the Boltzmann distribution in therm equilibrium. The relative mole composition obtained from a poly(styrene)-poly(isoprene) diblock copolymer matches well with the known value.