In order to solve the problems of the optimal domains sequence choice without considering, overhigh resources occupied ratio and the unappeasable requirements of real- time quality of service (QoS), which cannot be settled by the conventional multipoint to multipoint (MP2MP) routing and wavelength assignment (RWA) algorithms in multi- domain optical networks, a kind of multi- core node shared tree RWA heuristic algorithm (MSTDC) is proposed. The calculation can be parallelized. The delay and minimal cost can be constrained for multi- domain optical networks. The multi- domain problem is transformed into single domain by the algorithm from constructing a virtual topology. So it can realize the accurate calculation of number and the hosted domains of the mininlized cores. The source and destination nodes are added in different shared trees with delay constrained algorithms according to specific QoS selection strategy， respectively. The performance of the algorithm is demonstrated in a multi- domain optical networks topology with fifty routing nodes uniformly distributed in nine domains, and the simulation results show that the wavelength occupied ratio descends 51.1%, the success ratio of the route ascends 24.8% and running time of the algorithm descends 64.6%.