Pain perception is strongly influenced by neural states preceding stimulus onset, yet whether such preparatory states can be causally reshaped remains unclear. Using a double-blind design, we tested whether closed-loop neurofeedback can reconfigure preparatory brain dynamics to influence subsequent pain processing. Real, but not sham, feedback enabled learning-dependent enhancement of pre-stimulus α oscillations in primary somatosensory cortex and their trans-hemispheric propagation. Training also selectively reduced transitions between EEG microstates associated with salience and attentional control, indicating reorganization of preparatory brain states. These neural changes were accompanied by attenuated pain-evoked cortical responses and reduced pain perception. Sequential mediation analyses further revealed that somatosensory α enhancement predicted microstate reorganization, which in turn suppressed pain-evoked responses. Together, these findings demonstrate that closed-loop neurofeedback can causally reshape preparatory brain states to bias subsequent sensory processing.