Abstract: Aiming at the problem that the rotational response is difficult to measure in structural identification, an improved approximate algorithm based on generalized inverse matrix theory is developed for rotational response reconstruction. Starting from the basic equations of static condensation, the algorithm is available to calculate the rotational response in accordance to structural displacement data by solving the generalized inverse matrix. The applicable condition of generalized inverse approximate algorithm and the condition that the generalized inverse solution is just the accurate solution are discussed theoretically and given. Numerical examples are given to illustrate that the norm errors of the approximate algorithm is generally small, while the smaller the absolute value is, the greater the component errors will be.