Ablation cancer therapy using percutaneous intra-tumoral injection of ethanol is a promising method for targeted and effective locoregional cancer therapy. Magnetic gelatin microsphere (MGM) colloidal ethanol solution is developed as a potential injectable tumor ablation agent. The MGM was fabricated by electrostatic interactions among gelatin, acrylic acid, and acrylic acid-coated iron oxide nanoparticles. The fabricated MGM was dispersed in ethanol solution to form injectable MGM colloidal ethanol solution. The MGM colloidal ethanol solution can be easily infused and undergo gelation solvent exchange from ethanol to water in an artificial tissue. Furthermore, the MGM colloidal ethanol solution allowed doxorubicin (Dox) chemo-agent loading and its sustained release upon the formation of a drug depot by gelation in artificial tissues. Our study demonstrated that locally delivered ethanol and Dox with MGM colloidal ethanol solution promoted the anti-cancer therapeutic efficacy with a significantly suppressed cancer cell recovery rate. Overall, our developed injectable MGM colloidal ethanol solution that can be transformed to a hydrogel drug depot at the injection site holds clinical potential for a new class of chemo-ablation agents.