As to sensitivity analysis, based on traditional sensitive factor definition and concept of reliability vector, two kinds of sensitivity problems are putted forward in this paper. And factor sensitivity matrix is defined. As far as large and complex structures are concerned, factor sensitivity matrix of incremental form is given. Furthermore, sensitivity surface is putted forward. ANSYS PDS（ANSYS Probabilistic Design System）can solve the above two kinds of sensitivity problems efficiently. The example bridge is a CFST arch bridge with 83.6 meter-span, which operated for 10 years. The analysis result shows that the definitions enhance the maneuverability of sensitivity analysis, and ANSYS PDS is practical.