Aero-engine casings are important connecting and bearing components in aero-engine. Because of their complex structures， weak rigidity and difficult-to-machining materials， there are many manufacturing problems remaining for casing part such as serious machining deformation and poor accuracy of wall thickness， which has become a bottleneck restricting the development and production of new aero-engines. Aiming at this requirement， we propose a new method named counter-rotating electrochemical machining （CRECM）. During CRECM， a revolving cathode tool is used， and the anode workpiece and cathode tool rotate oppositely at the same rotational speed. As the material is dissolved accurately layer by layer in CRECM， the large thin-walled casing part can be machined precisely without deformation. The fundamental scientific problems involved in CRECM such as the anode shaping rule， the pulse dynamic dissolution mechanism of difficult-to-cut materials and the distribution characteristics of electrolyte flow field are revealed. The key technologies such as cathode tool design， pitting inhibition of titanium alloy and optimization design of electrolyte flow field are broken through. Moreover， a large-scale CRECM machine with independent intellectual property rights has been developed， and large thin-wall casing parts are fabricated efficiently and precisely. The research provides important technical support for the development and production of new aero-engines.