The harmonic convergence of service-oriented computing and grid results in the emergence of service grid and makes grid technology evolve into business domain. Along this evolution, the problem of transaction support becomes crucial because it is transaction that determines the adoption and success of business grid applications at most time. However, existing transaction models are not applicable in service grid environment. Though many new models have been suggested, they still have some deficiencies. In this paper, a new model is proposed based on the analysis of existing work. Take the behavior of services, the interdependence between them and the high-level requirement on transaction properties as the starting points, the proposed model is easy to implement and suitable for grid environment.