This paper proposes an observation-based control approach with only local sensing for controlling a team of nonholonomic mobile robots to keep predetermined geometric shapes. Based on the data from the encoders and CCD cameras, each follower keeps formation by observing its leader. Considering that the error accumulation of the encoders, only several recently sampling information are employed and a multi-step recursive prediction strategy is introduced. The local cooperation emerge by observation is without the need of global knowledge, especially suitable for the case of communication failure. The experiments show the validity of the proposed approach.