The invention provides a two-dimensional error compensation device for grinding titanium alloy casting circular hole cavities and a method. The method comprises the steps that an electric spindle is gripped by a robot with a force control sensor, the titanium alloy casting circular hole cavities are ground with different rotary files, the surface profiles of the titanium alloy casting circular hole cavities are measured with the force control sensor firstly before grinding is conducted, then errors perpendicular to the machining face direction and errors in the machining face direction are compensated according to a measurement result, and grinding on the bottom planes and cylindrical surfaces of the titanium alloy casting circular hole cavities is achieved. The actual profiles of the titanium alloy casting circular hole cavities are detected online, two-dimensional error compensation is conducted on each titanium alloy casting circular hole cavity, the machining amount can be determined, the feeding paths can be reduced, and the surface quality can be improved. Therefore, the two-dimensional error compensation device has the wide application prospect in titanium alloy casting circular hole cavity machining, the production efficiency can be improved, and considerable benefit can be brought to an enterprise.