The effects of hydroxyethyl cellulose（HEC） and hydroxyethyl methyl cellulose with high and low substitution degree （H-HEMC， L-HEMC） on the early hydration process and hydration products of calcium sulphoaluminate（CSA） cement were studied. The results show that different dosages of L-HEMC can promote the hydration of CSA cement from 45.0 min to 10.0 hours. All the three kinds of cellulose ethers firstly delay the hydration of CSA cement during the dissolution and transformation stage， and then promote the hydration of CSA cement from 2.0 hours to 10.0 hours. The introduction of methyl group enhances the hydration promotion effect of cellulose ether on CSA cement， and the promoting effect of L-HEMC is the strongest. There are significant differences in the effect of different substituent groups and substitution degree on the production of hydration products produced within 12.0 hours. The promotion effect of HEMC on hydration products is stronger than that of HEC. The amount of ettringite and aluminium hydroxide generated in L-HEMC modified cement paste are the most at hydration for 2.0 hours and 4.0 hours.