In view of special engineering properties of red clay and the waste of phosphogypsum solid-waste resource, the compression characteristics of phosphogypsum-stabilized red clay under different mixing ratios were studied through consolidation tests with cement as curing agent. And the mechanism of compressive modulus change law was analyzed based on microstructure and mineral composition. The results show that plain red clay presents medium compressibility, while phosphogypsum-stabilized red clay presents medium and low compressibility. The compressive modulus of mixture increases first and then decreases with the increase of phosphogypsum content. The compressive modulus is the largest as the mass ratio of cement to phosphogypsum is 1∶3. The degree of influence on the compressive modulus of mixture is vertical load>cement content>phosphogypsum content. The compressive modulus of mixture can be fitted by a binary cubic function relationship with cement content and phosphogypsum content. With the increase of phosphogypsum content, the hydration reaction, adsorption of cement and the formation of ettringite reduce the porosity of the mixture. When the mass ratio of cement to phosphogypsum is 1∶3, the porosity is minimum. When the content of phosphogypsum continues to increase, the solution is acidic, ettringite is dissolved, the content of free iron oxide decreases, the cementation and mechanical bite of aggregates are reduced, and the compression modulus is reduced.