Abstract: As one of the approaches to so called Ideal Observation & Measurement Technique (IOMT) for the fluid mechanics and the most practical one of Full Flow Field Observation and Measurement techniques (FFFOM) which will be the new generation of the experimental technique or instrumentation to across the new century, the recent progress and trend of Particle Image Velocimetry (PIV) & its application (including some works in China) are summarized and evaluated in some aspects.Also the facing requirements and further work of PIV for the complex & turbulent flows and the industrial applications are discussed. It will be the challenge for the PIV to face 21st century.