In order to explore the influence of the number of cascade stages of the same structure cascade sensor on the sensitivity of the sensor， a comparative study on the same structure based two-stage and three-stage cascaded Mach-Zehnder（M-Z） optical fiber sensor was carried. In the experiment， we fabricated the two-stage cascaded and three-stage cascaded M-Z sensor based on the waist-enlarged structure and misaligned structure. In order to study the difference between the two-stage cascaded structure and three-stage cascaded structure， the strain performance was also measured. The experimental results show that the strain sensitivity of the two-stage cascaded M-Z sensor with waist-enlarged structure is -0.76 pm/με， and that of the three-stage cascaded M-Z sensor is -0.75 pm/με， the sensitivity change of strain is 0.01 pm/με. The strain sensitivity of the two-stage cascaded M-Z sensor with misaligned structure is -0.73 pm/με， and that of the three-stage cascaded M-Z sensor is -0.77 pm/με， the sensitivity change of strain is 0.04 pm/με. Therefore， the sensitivity of the three-stage cascaded structure is not improved obviously compared with the two-stage cascaded structure. The study shows that the multiple cascaded M-Z structures can not improve the sensitivity.