Estimation　efficiency　is　one　of　key　topics　in　computationally　intense　optical　flow　algorithm.　Traditional　numerical　iterative　methods　are　effective　at　eliminating　the　high　frequency　components　of　the　estimation　error,　while　keeping　most　of　low　frequency　components　unchanged.　In　this　paper,　we　consider　the　multi-grid　based　real-time　implementation　of　dense　optical　flow　computation　by　classical　Horn-Schunck　model.　For　this　purpose,　establishing　of　the　linear　set　of　equation,　which　is　required　in　linear　multi-grid　model,　is　carefully　studied,　and　the　overall　multi-grid　framework　is　presented.　Efficiency　and　effectiveness　of　the　proposed　algorithm　is　validated　by　experimental　results.