Abstract: In order to select the precocious strain of the E.necatrix and understand the reproduction,further develop the anti-chicken coccidiosis precocious attenuation vaccine on the basic characteristics of the precocious strain.One strain was isolated and identified as P0 using the single oocyst isolation technique and selected for precocious strain through 8 generations as P8.The 11-day chickens were challenged with P0 and P8 separately at 0.05×104，0.1×104，0.5×104 and 1.0×104 per-merely，detecting the reproduction 7～13 post-challenge everyday.Both the reproduction of P0 and P8 were highest at 0.5×104 per-merely；the average gross output value of P8 was 55% of P0 ;the oocyst fastigium of P8 was ahead of P0.

Key words: E.necatrix; isolation and identification; selection of precocious strain; reproduction