Abstract　  

   The launched of the Chandra and XMM-Newton Observatories allowed us to study stellar accreting X-ray sources in external in great details. With the increase in the source number in each of the nearby galaxies, we are now in the position to study the statistical properties of these sources and their population dynamics. In this talk I shall discuss the population dynamics of accreting X-ray sources in external galaxies and how the dynamics determine the observed luminosity function. I shall present a semi-analytic model for the X-ray source luminosity functions and how we can use this to study X-ray sources in young galaxies at high red-shift. I shall also discuss how to recover the underlying source populations in multiple observations and the implications of modelling X-ray source luminosity function on a wider astrophysical context, such as galaxy evolution and cosmology.