The optical tweezers are convenient tools for investigation of mechanical characteristic of biological particle. The elasticity of red cell membrane is an important index for people to appraise the ability of blood transporting oxygen. Using single optical tweezers technology, a new method to measure the elasticity of RBC membrane was established. Adopting this new method, the elasticity of normal RBC membrane was detected and were consistent with the results of double optical tweezers method. Moreover, the membrane elasticity for RBC with phenylarsine oxide (PAO) was measured. The result displayed a linear relationship between elasticity decrease and increase of PAO concentration. Therefore, this new method has high sensitivity and is acceptable.