A new calculation method of Abel transformation is described for transforming observed radiances into the radial distribution of emission coefficients of plasmas. The characteristic of this method lies in transforming improper integral into the usual one. Thus various kinds of usual approximate integrals can be used, and the observed data may be calculated directly and conveniently to obtain necessary numerical accuracy. The method may be applied to cylindrically or spherically symmetric and optically thin plasma often encountered in plasma physics and astrophysics.