A truss’ reactions often need to be solved after the structure is calculated by matrix displacement method. It is inconvenience that the rational solution based on the truss axial force needs to determine the sign of sum terms according to whether the beginning joint or the ending joint is connected to the support. But if the convention is changed to matrix displacement method, a new reaction formula based on element-end forces can be deduced and efficiently solve the deficiency, and then, can also decrease the complication in teaching and programming.