In order to increase the spectrum utilization in elastic optical networks(EON), an adaptive modulation and fragmentaware shared path protection algorithm is proposed. The proposed algorithm uses the spectrum block bearing weight (SBBW) to measure the ability of connection establishment for different spectrum blocks, and prefers the paths including links with larger SBBW as candidate working paths. The working path is established by choosing the spectrum block with the minimum difference of SBBW before and after the allocation. Then, the proposed algorithm selects the paths containing links with larger weight of both available spectrum block and protection spectrum block as candidate protection paths. The proposed algorithm prefers to use the protection spectrum block with the smallest SBBW difference before and after the allocation to establish the protection path. When the establishment fails, the available spectrum blocks with the minimum difference of SBBW before and after the allocation are selected to establish the protection path. Simulation results show that the proposed algorithm can reduce the bandwidth blocking probability, spectrum fragmentation ratio and spare capacity redundancy.