Small turbines must operate at high rotational speeds to generate adequate output power. In this study, a radial inflow turbine using R245fa as the working fluid is miniaturised and is designed to have a rotational speed of 30,000 r/min. The organic Rankine cycle system is not simplified, and a preheater and a superheater are installed. The turbine is experimentally analysed in the organic Rankine cycle system. The experimental results show that with an increase in the inlet pressure, the turbine output power and system efficiency increase; moreover, the turbine efficiency first decreases and then increases slightly after the pressure exceeds 1.5 MPa. The turbine efficiency decreases first and then increases and attains the minimum value at an inlet temperature of 100°C–105°C. When the flow rate is 0.82 m3/s, the speed reaches its maximum value of 28,000 r/min, and a maximum output power of 17.37 kW is generated. The maximum efficiency of the turbine is 0.885 and that of the system is 0.1625. The experimental data and design parameters of the turbine provide a reference for further design optimization.