The search for targets in a large range of sector of airborne fire control radar is usually conducted in four-line scanning mode.In order to discover the targets earlier than the traditional progressive scanning can do, a four-line flyback scanning mode is proposed.Suppose that the target may appear in every position of the searched sector, and the coordinates conform to a two-dimensional uniform distribution.Based on the assumption of discovery probability model in a single scanning, the expected discovery time of the two scanning modes is calculated by using the Monte Carlo method.The simulation results show that the expected discovery time of the flyback scanning mode is less than that of the progressive scanning mode in one scanning period of radar.That is to say, the flyback scanning mode can realize target discovery faster than the traditional progressive scanning mode in statistical sense.