A novel method consisting of fault detection, rough set generation, element isolation and parameter estimation is presented for multiplefault diagnosis on analog circuit under tolerance. Firstly, a linearprogramming concept is developed to transform the fault detection of circuit with limited accessible terminals for measurement to check existence of a feasible solution under tolerance constraints. Secondly, the fault characteristic equation is deduced to generate a fault rough set. It is proved that the node voltage of nominal circuit can be used in fault characteristic equation under tolerance. Finally, fault detection of circuit with revised deviation restriction for suspected fault components is proceeded to locate faulty elements and estimate their parameters. The diagnosis accuracy and parameter identification precision of the method are verified by simulation results.