Disclosed is a treatment system for the slag phase after removing iron-aluminum-chromium from leaching solution of laterite nickel ore, which relates to the technical field of slag phase treatment of laterite nickel ore and comprises a filtering module, a refining module, a feeding module, and a measurement module. The filtering module comprises a material suction component and a filtering assembly. The material suction component is positioned within a slag phase sedimentation zone of a multi-stage removing iron-aluminum-chromium unit, with its material suction inlet connected to the slag phase sedimentation zone. The filtering assembly is connected to the outlet of the material suction component and features a filter residue outlet and a filtrate outlet. The refining module is connected to the filter residue outlet. The feeding module consists of a material pipe and a material guiding drive component. The material pipe has an inlet end connected to the outlet of the refining module. A measurement module is connected to the material guiding drive component and the neutralization unit. This setup enables the timely filtration of the generated slag phase, followed by refinement processing, and allows for the controlled metering of the returned filter residue. Consequently, it enhances the subsequent acid leaching and dissolution efficiency of the slag phase.