Abstract: In this paper, we briefly review the theory of sensitivity analysis of Generalized Geometric Programming Problem (GGPP), and then put forward a practical algorithm to solve sensitivity analysis of difficult GGPP. We use a "L" type gantry crane's mathematical model of the optimal design as an example, to analyze influences on optimal solutions of the model when its parameters such as crane's hoisting capacity, span, metal materials, etc. have been perturbed. The analysis results are useful for practical engineering design.