  We have theoretically investigated a general function photonic crystals
(GFPCs) with defect layer, and choose the line refractive index function for
two mediums $A$ and $B$, and analyze the effect of defect layer's position,
refractive indexes and period numbers on the transmission intensity and the
electric field distribution. We obtain some new characters that are different
from the conventional PCs, which should be helpful in the design of photonic
crystals.
