The　fluctuating　heat　sources　and　seasonal　condensing　environments　are　critical　to　the　operation　of　Organic　Rankine　Cycle　(ORC)　under　off-design　conditions.　This　paper　presents　a　comprehensive　steady-state　mathematical　model　developed　using　a　newly　built　experimental　platform.　Focusing　on　the　operational　characteristics,　including　the　evaporation　pressure,　condensation　temperature,　mass　flow　rate,　and　the　performance　of　key　equipment　during　the　regulation　of　the　expander,　working　fluid　pump,　and　cooling　water　pump.　Results　show　that　the　net　efficiency　initially　increases　before　decreases,　with　both　evaporation　pressure　and　mass　flow　rate　rising　alongside　the　working　fluid　pump　frequency.　The　quasi-two-stage　single　screw　expander　achieves　an　isentropic　efficiency　above　65　%.　Additionally,　flexible　adjustments　to　the　cooling　water　pump　effectively　regulate　the　cooling　system,　with　timely　cleaning　of　cooling　pipelines　enhancing　net　efficiency　by　up　to　3.27　%.　Optimization　using　the　particle　swarm　algorithm　improves　system　performance,　achieving　net　efficiency　enhancements　of　1.8　%　and　12.3　%　under　specific　conditions.　The　novelty　of　this　study　lies　in　directly　regulation　of　the　expander,　working　fluid　pump,　and　cooling　water　pump,　significantly　enhancing　the　off-design　performance.　This　research　provides　valuable　insights　for　researchers　and　designers,　enabling　flexible　regulation　of　ORC　operations　to　ensure　efficient　performance　under　varying　conditions.