The catalyst support is an important part of the load-type catalyst. As an active substance with good dispersibility in the skeleton, it can not only increase the strength of the catalyst but also serve as an active center. In addition, the pore structure and specific surface area of the support also have a great influence on the catalytic performance of the catalyst. Therefore, it is necessary to study the structure of the catalyst support. In the catalytic dimerization of propylene to produce 4-methyl-1-pentene (4MP1), 4MP1 is a thermodynamically unstable product, which is extremely easy to be converted into other thermodynamically more stable byproducts. Moreover, the distribution of propylene dimerization products is complex, and the equilibrium conversion rate of each reaction is close to 100%, with a high degree of spontaneity. Therefore, in order to improve the selectivity of 4MP1, a suitable catalyst system should be selected. Solid base catalyst has been widely used in the dipolymerization of propylene to 4MP1 because of its high selectivity and ability to inhibit isomerization. Alkali metal K was supported by alkali metal carbonate, alkali metal bicarbonate, alkaline earth metal carbonate, and alumina of different crystalline forms to prepare solid superbase catalysts for propylene dimerization to 4MP1. The role of catalyst support in the process of 4MP1 formation and the influence of different support properties were systematically summarized. The specific surface area and pore diameter distribution of the carrier material were characterized by a mercury injection meter and scanning electron microscope (SEM). The results showed that the internal diffusion resistance was caused by the pore structure of different carriers, which affected the product distribution of the propylene dimerization reaction. When the target product of the dimerization reaction was 4MP1, the catalyst prepared by using K2CO3 as the support to support alkali metal K had a good 4MP1 selectivity, up to 87.38%. For the propylene dimerization reaction path and 4MP1 isomerization reaction, the material with low specific surface area, large pore diameter, and narrow pore diameter distribution should be preferred as the carrier for the high selectivity of propylene dimerization 4MP1.