In order to reduce the calculation in robotic arm allocation, the invention provides a spherical linkage type surgical robotic arm, which includes a first curved bar having a first axis center and a second axis center, a second curved bar being equal to the first curved bar in length and having a third axis center and a fourth axis center, the third axis center in coincidence with the first axis center, a third curved bar having a fifth axis center and a sixth axis center and being pivoted to the second curved bar, and a fourth curved bar having a seventh axis center and an eighth axis center and being pivoted to the third curved bar and the first curved bar, thereby reducing the calculation burden and facilitating control and allocation.