In order to expand the comprehensive utilization of phosphogypsum, raw phosphogypsum (RPG) and β-hemihydrate phosphogypsum (HPG) were used as main raw materials. Besides, metakaolin (MK) and alkaline activators (quicklime, water glass) were used to modify and prepare a kind of phosphogypsum-based composite gelling materials. The effects of MK content, water glass content and the relative ratio of RPG and HPG on mechanical properties, water resistance and dry and wet resistance of metakaolin-phosphogypsum-based composite gelling material (MKPGBM) were investigated by single-factor tests. The mechanism was also analyzed at last. The results show that the strength of MKPGBM can be effectively improved by increasing the content of MK, water glass and HPG. The mechanical properties and water resistance of MKPGBM are optimal when the content of MK and water glass (by mass fraction) are 7%~9% and 21%~24%, respectively. When the relative ratio of RPG and HPG is 5∶5 (mass fraction ratio), the 28 d compressive and flexural strength of MKPGBM are the best, which are 19.58 and 7.44 MPa, respectively. The overall performance of MKPGBM is better when the relative ratio of RPG and HPG is 6∶4, and its 28 d softening coefficient reaches 0.796. The incorporation of MK and admixtures can effectively promote the formation of hydration products and fill the pores between matrix, and can also improve the mutual contact strength of RPG internal particles, thereby improving the mechanical properties，water resistance and dry and wet resistance of phosphogypsum-based composite gelling materials.