For general reliability analysis with fuzzy failure region F % , the general failure probability F P% is defined as the integral of product of μF% [g( y)] , the membership of performance function ( ) g y to F % , and joint Probability Density Function (PDF) f ( y) over , the total variable space, i.e. [ ( )] ( ) F F P μ g f d % = ∫ ∫ % y y y L . On the basis of line sampling, an efficient method for random failure probability analysis with clear failure region, a new numerical method is presented to calculate F P% . In the presented method, the total integral region is split into m clear sub-regions i F in a way that the value of g( y) in i F can be approximately viewed as i g , a constant independent of y , and the value of [ ( )] F μ % g y in i F can be viewed as a constant ( ) F i μ g % subsequently. Due to the closely invariant property of [ ( )] F μ g % x in i F and 1 2 m = F I F ILI F , F P% is transformed into the sum of ( ) F i μ g % ( ) i F ∫L∫ f y dy , where ( ) i F ∫L∫ f y dy is the random failure probability with the clear failure region i F and can be obtained by line sampling. The high efficiency of the presented method resulted from that of the line sampling is demonstrated by the illustration.