Rheological properties, printability, and 3D printed geometries texture of soy protein isolate (SPI) mixtures with sodium alginate and gelatin were investigated. The SPI and their mixtures showed shear-thinning behavior and can be used as an ideal material for 3D printing. Comparing with SPI, the viscosity and elastic modulus for SPI mixture with gelatin were lower at 35 degrees C, while the rheological index increased quickly as temperature decreased to 25 degrees C which supported the deposited layers and kept the designed shape. The SPI mixtures with 2, 6, and 10% gelatin could print excellent geometries. The addition of sodium alginate and gelatin to SPI didn't cause chemical cross-linking between protein subunits during mixing and 3D printing at 35 degrees C, while improved the hardness and chewiness of 3D printed geometries. The overall results suggested that the food matrix of SPI, sodium alginate and gelatin will be a promising material in 3D food printing.