A vectorial effective index method is used to design photonic crystal fibers with flattened dispersion around 800 nm. The dispersion of photonic crystal fibers is obtained by the sum of material dispersion and waveguide dispersion, and the latter can be varied by the scaling property. The flattened dispersion is designed to be around the operating wavelength of the widely used Ti： sapphire femtosecond lasers, holding much promise for the study of propagation of ultrashort laser pulses in such fibers.