Abstract: Based on abundant data,the author systematically discusses the sedimentary environment,diagenesis,and organic evolution of Cambrian-Ordovician carbonate rocks in north China,suggesting that foreslope,open-marine and limited marine facies are favourable fa-cies of source rocks,with micritic limestones,biolithite and dolomitic limestone as main source rock assemblage,and the upper Xinji Formation of Cambrian,lower Majia Gou and Fengfeng Formations of middle Ordovician as major source rocks.