In view of the convenience and effectiveness of a position sensitive detector (PSD) in sensing the local distortion of a light beam wavefront, a high-speed wavefront sensor based on PSD array is proposed, fabricated and characterized. As a prototype of this kind of wavefront sensor it consists of a matrix of 4×4 tetra-lateral PSDs, and each PSD unit measures 500 μm×500 μm with a 300 μm interval between them. Each unit has 4 electrodes, which can be used for photocurrent output. The local distortion of a light beam wavefront can be deduced from those 4 photocurrents. Besides 64 electrodes of 16 element units, the sensor also has another common electrode that can be used in applying a reverse bias. Primary tests of the device show that it has low dark current, high spectral sensitivity, very fast response speed, and quite small crosstalk between its neighbouring units. The dark current of an element unit is less than 1 nA at a reverse bias of 20 V. The peak spectral sensitivity of the sensor is over 0.6 mA / mW at 900 nm wavelength. Its response time is about 10 ns at 45 V reverse bias, and the crosstalk between its neighbouring units is as low as 1.6% at λ= 650 nm and Ur = 5 V.© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.