A kind of generalized matching theory is proposed for multi-port networks

and the concrete method for realizing is given. The study shows that to perfectly match a network

the transmission of the network must be sacrificed in certain degree. Particularly

if the network is complete symmetrical

the module of transmission coefficient should satisfy the unequality |β|<1/（N- 1）. In addition

we found the phenomenon that sudden changes will occur in the generalized matching of three-port reciprocal networks when the network changes from lossy to lossless

which deserves a further research.