In the photoassociation reaction I + H -> HI induced by the ultra-short laser pulse, the two collision atoms, I and H, can combine into a molecule with a selective vibrational state. The state-selective population of the product molecule HI depends on the laser pulse parameters and the relative collision momentum of the two collision atoms. The theoretical calculations show that the optimal laser pulse parameters, such as the duration, intensity and frequency, can be used to control the vibrational state-selective population of the product molecule. (c) 2006 Elsevier B.V. All rights reserved.