The focusing and leveling system which is based on scanning mirror modulation and triangulation principle is introduced. This system follows the SCheimpflug（ SC） imaging condition and measures the focal plane displacement of silicon by detecting the displacement of the projection slit spot relative to the detect slit. In order to improve the anti-jamming ability

the system uses a scanning mirror to modulate the optical signal. It is found that the system has precision of nanometer

and it has the characteristics of high sampling frequency

non-contact

and easy multiple-beam layout.