Atechnique for analytic evaluation of one-dimension Huygens' integral is proposed. The sound fields of the parametric line array can be analysed by it. Firstly, the point-source function is expanded into an operator on a plane wave function. Putting it into above mentioned integral and calculating it, it is shown that if we make an operation of this operator on the far-field solution, a general expression of radiation from parametric line array can be obtained. Secondly, both Fraunhofer's far-field approximation expression and Fresnel's, nearfield approximation expression are derived from it, but the latter approximation make a appreciable contribution on the radiation only outside the range of half-width angle.Furthermore; the radiation of a truncated parametric line array whose length is R1 is caleucated. We find that the beam pattern of this array becomes more narrow as decreasing the range. And a prediction can be made that the radiation field of a real parametric array will depend on following three parameters: kR sin2θ, βR, R1. Finally, basing on this theory, it appears to the author that the inconsistencies in ap-pearenee for some published experiments can be consistent with each other.