For ascertain changing rules of machined surface profile in orthogonal turn-milling,the macroscopic profile of machined surface in orthogonal turn-milling was researched.The simulation algorithm of machined surface macroscopic profile in orthogonal turn-milling was built.Three dimensional graphics of machined surface macroscopic profile corresponding to cutting parameters were simulated and changing rules of those were analyzed.Finally,above simulation results were verified by some experiments.The above work reflect the changing rules of machined surface macroscopic profile in orthogonal turn-milling,it offers a reference for improving cutting precision of orthogonal turn-milling.