The spontaneous changes in cell shape and size, the membrane bending elastic modulus, and the structure and functions of intracellular hemoglobin of single human living erythrocyte incubated in different suspension pH were studied. The non-invasive,in situ, real time measurements on the parameters at the three levels of intracellular molecule, membrane and cell morphology were performed simultaneously by using a fast micro-image analyzing technology and a multi-channel micro-spectrophotometer system. The result shows that the cell shape and size, the mechanical property of the cell membrane, and the structure and function of intracellular hemoglobin are correlated and affected by each other with pH.