The present invention relates to the field of rubbers, particularly to a liquid trans-polycyclopentene rubber, a preparation method and applications thereof, wherein the number average molecular weight is 800-60000, the molecular weight distribution index is 1.1-3.5, the straight chain structure content in the polymer is more than 99 wt%, the trans structure content is more than 70 wt%, the glass transition temperature is less than -85 DEG C, and the gel content is less than 0.02 wt%. According to the present invention, the liquid trans-polycyclopentene rubber has the inherent excellent characteristics of the liquid rubber, the rubber prepared by mixing the liquid trans-polycyclopentene rubber and other types of rubbers can provide performances of good processability, good extrusion performance, good low-temperature resistance, high resilience, low heat-generation, high wear resistance and the like, and the catalyst preparation step and the rubber preparation process are separated in the liquid trans-polycyclopentene rubber preparation method, such that the stable product catalyst can be separately prepared and can be prepared in advance and is easy to store, and the method is suitable for industrial production.