The traditional method of calculation for the acceptance parameters by Taylor expansion in three wave interactions is only suitable for the condition of small acceptance parameters. The accurate calculation method of the acceptance parameters by means of definition is given. Through numerical calculation some values of acceptance parameters are corrected, and some super wide acceptance wavelength bands of SHG in nonlinear crystals are found, which are almost tens times larger than that calculated by traditional method. It suggests the possibility of obtaining super acceptance spectral bands in 1 cm long crystal for SHG.