In order to develop a simple and efficient protocol for isolating total RNA from thalli of Porphyra haitanensis, three methods(CTAB method, SDS method, Guanidine thiocyante method) which were commonly used to isolate and purify total RNA were improved based on the methods of wiping off polysaccharides and polyphenol， and absorbency method, electrophoresis method and RT-PCR method were employed to determine the quality and quantity of RNA. RNA isolated by spin column kit method and RNAiso method was also compared with the RNA by the three methods. The results show the total RNA isolated by SDS method, guanidine thiocyante method and RNAiso method was of poor purity, retained some protein and polysaccharide and some RNA have dissolved into single nucleotide acid. But the total RNA which isolated by CTAB method and spin column kit method was of good quality and high purity, the substance which can restrain the active of reverse transcription enzyme also was cleared. These results suggest that CTAB method and spin column kit method are fit for the isolation of total RNA from the thalli of P.haitanensis, but each of the two methods has its advantages and disadvantages, we should choose the appropriate method based on the situation.