Based on 2.0L spark ignition direct-injection(SIDI) turbo charged gasoline engine with variable valve timing(VVT), the spark timing effects on combustion process, fuel consumption, knock limitation and emissions were studied with external exhaust gas recirculation(EGR) on different loads and speeds. For the purpose of easily comparing data results, the location of 50% mass fraction burned(CA50) was widely used in this paper. The study results show that CA50 is changing linearly with spark timing. To reach the same combustion phase, spark timing need to be further advanced with external EGR. Combustion variability of IMEP(COV) increase sharply with retarding of CA50 with external EGR. The external EGR can greatly improve knock limitation and knock intensity(KI). To reach the best fuel consumption, CA50 need to be advanced to 6 °CA to 8 °CA for both with external EGR and without external EGR. NOx emissions increase with advancing of spark timing. HC show different trends when retarding spark timing with and without external EGR.