Good die surface shapes improve the flow pattern of the tube material, reduce stress concentration of the products, and decrease the forming load. The objective of this paper is to propose a design guideline for die surface shapes in T-shape protrusion hydroforming of magnesium alloys with different outlet diameters and propose an adaptive control algorithm to determine appropriate loading paths for the forming process. The finite element analysis is used to simulate the flow pattern of the tube during tube hydroforming process. The analytical flow line distribution of the tube is utilized to determine the speed ratio of the counter punch to the axial feeding at the protrusion stage of the hydroforming process. Experiments of T-shape warm hydroforming of magnesium alloy AZ61 tubes with a 1/2 outlet diameter ratio are conducted. Loading paths determined by the proposed adaptive simulation algorithm is adopted in the tube hydroforming (THF) experiments. From the comparisons of the product shape, thickness distribution, and flow line configuration between the analytical and experimental values, the validity of the proposed die design guidelines and control algorithms is verified.