In order to screen the optimal extraction method of total RNA from each tissue of fennel,in this study,the fennel from Haiyuan in Ningxia was used as the material,modified hexadecyl trimethyl ammonium bromide(CTAB) method,CTAB water saturated phenol method,modified Trizol method and OMEGA plant RNA extraction kit (the kit method for short) were compared in the effects of total RNA extraction from roots,stems,leaves,flowers and seeds of fennel.The concentration,purity and integrity of total RNA from each tissue of fennel were determinated by nucleic acid and protein detector as well as agarose gel electrophoresis.The results showed that for fennel roots,steams,leaves and flowers,the quality of RNA extracted by the kit method was the best,the yield was higher,and the extraction time was short.The quality of RNA extracted by the modified CTAB method was better,the yield was high,but the extraction time was longer.The yield of RNA extracted by the modified Trizol method was higher,but the concentration and integrity were poor.The yield and quality of RNA extracted by the CTAB water saturated phenol method were lower. For fennel seeds,the effect of RNA extraction by the modified CTAB was the best.