The first criticality of the China Experimental Fast Reactor（CEFR）was reached on July 21，2010. The CEFR is the first step in fast reactor engineering development in China, which was launched in the framework of The National High-Tech Program. The design and construction timetable, the main design characteristics and the parameters of the CEFR are briefly introduced in the paper. Emphasis is placed on describing the criticality calculation tools and results before its physics start-up and then the physics start-up testing process and results are described. Finally some important experiments completed at the reactor criticality state are listed.