The basic principle of parallel confocal detecting method is proposed. With the 3-D point spread function and the matrix operating form, the mathematical model of 3-D detecting process based on the method is established, which has a higher theoretic value and a wider suitability due to the involvement of the general confocal and non-confocal detection. Meanwhile, the conclusion of theoretical analysis shows that the optical detection of parallel confocal method conforms to the multiplication form of two point spread functions, which is the fundamental characteristic of confocal detection.