Electrical capacitance tomography（ECT）system for voidage measurement is described.Voidage measure-ment principle based on ECT is analyzed.Three modeling methods for voidage measurement

which are based on genetic algorithm-partial least square（GA-PLS）

ant system algorithm（ASA）

and least squares support vector machine（LS-SVM）respectively

are reviewed briefly.All the data under three voidage measurement methods come from the ECT sensor.A unifying model is put forward to provide a universal voidage measurement framework.The experimental data are used to evaluate the three methods in terms of generalization ability index

maximum measurement error

mean measurement error

and measurement time.The results show that the LS-SVM method has highest precision and best generalization ability.