High speed has been the desire of the rotorcraft industry all along. Novel configuration designs such as tilt rotors and compounds have extended speed envelope. Slow rotor at high advance ratios is a critical design characteristic when rotorcrafts reach large cruising speed. It is because that the speed of advancing blade tip is limited by compressing effect such as transonic shock and drag divergence for critical Mach number. It can reduce the compressibility effect and the profile power. However, a lot of uncommon aerodynamic phenomenon such as reversal thrust in the high advance ratios region (μ > 0.5) will appear. Furthermore, the rotor tracking and balancing is also a challenge because of augmenting effect for any rotor inconsistency. The aerodynamics of slow rotor at high advance ratios need be understood in order to develop next generation rotorcrafts. The predicting tool need also be developed to evaluate for the extreme flight conditions. The experimental test data is required for the representative rotor in these conditions. For these reasons, many tunnel tests have been carried out for the slow rotor. The paper provides a summary of the study on the slow speed at high advance ratios rotorcrafts firstly. Then, the slow rotor experimental test technique is described, consisting of the development history and implementation challenge. Finally, a prospect of the development for the slow rotor at high advance ratios test in the future is made.