The invention discloses a parallel routing optimization method under an elastic optical network. The method includes: step 1: when a batch of services arrive at the network, use the GPU to solve the shortest path for each service on its available hierarchical graph as Alternative path; Step 2: After calculating the alternative path, use the routing selection algorithm to select a route for the service; Step 3: Determine whether the service can be added to the network, if so, end the algorithm, if not, proceed to Step 4; Step Four: Determine whether the services that have not been added are all blocked services, if so, end the algorithm, and output the path selected by the service, if not, it is necessary to recalculate the route for the services that have not been added, and return to step 1; this method is sufficient Using the powerful parallel computing capability of GPU, the calculation speed of routing optimization algorithm is improved.