Semi-solid processing (SSP) technique is an important method for metal casting. Products made by SSP technique have advantages such as small solidification shrinkage, high dimensional accuracy of castings, fast forming speed, high productivity, and good mechanical properties. Aluminum alloy products produced by SSP technique can be heat-treated. The mechanical properties of the products after heat treatment are similar to those of steel, but they have the lighter mass and are widely used in many fields. Semi-solid slurry preparation technique is one of the key techniques in the field of aluminum alloy semi-solid forming, which determines the industrial application of semi-solid forming and also has significant impact on the quality of aluminum alloy semi-solid slurry. Semi-solid slurry preparation technique with the continuous development has become the emerging technique in the field of metal processing. The principles, advantages and disadvantages of various semi-solid slurry preparation techniques for metal materials were reviewed, and the future trends of semi-solid slurry preparation techniques were predicted.