An oblong-shaped rotor engine with improved high sealing performance includes an upper end cover, a lower end cover, a rotor, three combustion chambers, three isolation zones, a fuel spray ignition unit, a sealing pin row and an eccentric driving shaft, a sealing pin row, which seals the transition zone between different combustion cylinders, wherein the engine according to this invention can better avoid the effect of structural wear, effectively enhance the sealing performance between combustion chambers and abate gas leakage between cylinders, wherein the designed profile and sealing means can enlarge the design error margin for engines, abate the processing difficulty of engines, and effectively decrease the production costs of engines.