This paper pointed out that, for the design of continuous phase Fresnel lens, it helps to reduce control difficulty of the fabricated profile to replace the more complex quadratic profile with simpler linear one. The difference between such two kinds of profile was analyzed in details. By computer simulation, it was found that the optics transferring function (OTF) and the point spread function (SPF) of the linear profile lens are very close to the ideal ones,which provides the theoretical demonstration. At last, the further improving approach was pointed out.