The new series of Komatsu KTR 150 turbocharger was developed and added to its existing line of KTR 100 and KTR 130. A high efficiency mixed flow turbine and a backward swept compressor impeller is used in this turbocharger which is aimed at the diesel engines with the output range of 450~900 kw. This paper describes the methods of design and experiments of the mixed flow turbine. Experimental results by aerodynamometer showed that the mixed flow turbine has the high efficiency at large specific speed range. Rotating components were also verified to have sufficient reliability through experiments. Engine test results showed the substantial benefit in engine performance with this turbocharger.