This paper studied the flame initiation and early development in a spark ignition engine by using the Schlieren technique and a high speed camera. Some effects of different engine operating conditions and different spark energy are discussed. It was discovered that at any engine operating condition there exists a minimum flame propagation velocity during the early stage, and that its value as well as the corresponding time and flame radius can be used as a criterion to determine whether the early flame propagation is easy or not. To study the effects of different spark energy a special spark ignition system was designed which was controlled by a microcomputer for producing different spark energy levels. Both experimental and theoretical results show that the augmentation of breakdown energy in spark duration makes the original flame size increase effectively, which results in speeding up the flame kernel formation and early development. But, the augmentation of spark energy only during the arc and glow phases has no obvious effect.