With the two-impurity Anderson model Hamiltonian, we theoretically study the magneto-transport properties of the serially coupled double quantum dot system in a spin blockade regime, and solve Hamiltonian by the master equation approach. We find that the spin flip tunneling between dots due to the spin-orbit coupling can lift the quantum dot spin blocking. We also study the effects of the spin flip of quantum dots due to the hyperfine interactions and the spin exchange interaction on magnetic transport properties of the system. Some valuable results are obtained and the relevant problems are discussed.