Abstract: A general design principle and design method of non-uniform heating tube used in the critical heat flux （CHF） experiment with axial non-uniform heat flux distribution in full-scale bundle was introduced in this paper. Non-uniform heating tube in 5×5 full-scale bundle was designed according to this design principle and method. In fact the design of non-uniform heating tube is an optimizing design process considering various conditions such as the demand of power system, experiment technology, fabrication ability and welding technology. The final design result shall meet the needs of experiment as well as technological requirements. The non-uniform heating tube in 5×5 full-scale bundle according to this design principle has applied successfully in the experiment on CHF of fuel assembly.