Security constrained unit commitment (SCUC) is the most widely used model in power grid clearing scenarios. A solution framework for the super large SCUC spot market clearing problem is established. Firstly, the time decoupling solution method for SCUC problem is introduced, which is intended to reduce the size of the problem to accelerate the solving speed. Then a Lagrangian relaxation technique is proposed to solve the time decoupled subproblem, which effectively reduces the difficulty of solving key complex constraints without affecting the accuracy of the solution. Numerical experiments show that the proposed framework greatly improves the solution efficiency and is very stable.