The assembling and reconfiguration of the integrated devices are of great importance to extend the capability of photonic chips based on top-down fabrication approaches. Here, we demonstrate a fully-programmable organic micro-actuator for precise manipulation of on-chip microstructures. Controlled by a low-power laser, the micro-actuator achieves a 30 nm motion step size, and shows the capability to traverse various chip substrates, overcome obstacles, and push microspheres to target locations. The micro-actuator is applied to fine-tune the microcavity and shift the resonance by three linewidths without compromising its quality factor. This optically-driven micro-actuator offers a unique approach for post-fabrication assembly and reconfiguration of photonic circuits, paving the way for adaptive, multifunctional photonic systems.