The invention relates to a registration and alignment-based lineation-free forging-casting part machining positioning method. Since an aviation forging-casting part is complex in structure, smaller in machining margin and poor in blank consistency, if a traditional mode in which lineation is adopt to find machining references is used, problems such as poor positioning accuracy, low alignment efficiency and high rejection rate can be brought about, and those problems are the bottleneck of the machining of forging-casting piece blanks, and seriously hinder the intelligent, automated and numerical control development of the machining modes of forging-casting pieces. In order to solve the above problems, a measurement coordinate system and a machining coordinate system are unified; registration and alignment are performed on the digital model of the blanks and the CAD model of the blanks under residual constraint; a cutter location file is corrected through using a registration and alignment result; machining references can be determined accurately and automatically; after the accurate references are prepared, a lineation alignment auxiliary preparation process at a later stage is not required, and the prepared accurate references can be directly utilized to carry out quick and accurate positioning; and therefore, the automation degree and numerical control rate of the machining of the forging-casting piece blanks can be improved.