Multi-through　lanes　have　been　used　to　reduce　vehicle　delays　and　queue　lengths　at　signalized　intersections　with　relatively　high　through　movement　demands.　Limited　research　has　been　conducted　to　study　the　through　lane　group　capacity　issues　and　how　they　relate　to　the　number　of　lanes　in　the　through　lane　groups.　This　study　analyzed　the　influence　of　the　number　of　lanes　in　the　through　lane　group　using　11　sites　in　Beijing.　The　one-way　analysis　of　variance　(ANOVA)　test　was　used　to　determine　statistical　significance　of　the　number　of　lanes＇　influence　on　saturation　flow　rates.　In　addition,　regression　analysis　was　conducted　to　determine　the　relationship　between　the　number　of　lanes　in　the　through　lane　group　and　the　saturation　flow　rates.　The　results　showed　that　the　influence　of　the　number　of　lanes　in　the　through　lane　group　on　saturation　flow　rate　was　remarkable　in　Beijing.　The　relationship　between　saturation　flow　rate　and　the　number　of　lanes　in　the　through　lane　group　was　a　quadratic　function.　At　the　end　of　paper,　the　default　value　of　saturation　flow　rate　and　the　adjustment　factor　for　the　number　of　lanes　in　the　through　lane　group　was　given　based　on　the　traffic　conditions　in　Beijing.　©　2010　ASCE.