For sampled data controller design of nonlinear continuous time systems, it is important to derive a good approximate sampled data model because the exact sampled data model for nonlinear systems is often unavailable to the controller designers. Recently, Yuz and Goodwin have proposed a more accurate approximate model than the simple Euler model in the case of a zero-order hold. This paper derives an approximate sampled-data model for nonlinear systems using a fractional-order hold, and analyzes the sampling zero dynamics of the sampled-data model to show a condition which assures the stability of the sampling zero dynamics of the model. It is also shown that the stability of the sampling zero dynamics is improved compared with a zero-order hold.