The present invention relates to a method and system for allocating a dedicated protected spectrum based on crosstalk awareness, including calculation, core selection, a modulation format, and spectrum allocation. First, working paths are first established: selecting a modulation format; determining a maximum allowable crosstalk value, classifying cores, calculating inter-core crosstalk values of all available spectrum blocks, and selecting a spectrum block with the smallest crosstalk value for allocation; and then dedicated protection paths are established: selecting a modulation format; determining a maximum allowable crosstalk value, classifying cores, calculating inter-core crosstalk values of all available spectrum blocks, and selecting a spectrum block with the smallest crosstalk value for allocation. The present invention improves the spectrum resource efficiency of a space-division multiplexing elastic optical network, reduces a crosstalk value of each fiber link, and implements the survivability of a space-division multiplexing optical network.