We present a novel technique of temperature compensation for 3-dimensional fiber Bragg grating (FBG) strain sensor, and design a temperature compensation diaphragm for temperature compensation of the strain sensor by using reference optical fiber compensation method. Experiment results demonstrate that bare fiber without aging process can appear inflection temperatures between 30 ℃ to 40 ℃, which results in the decrease of the temperature sensitivity coefficient. So we must make aging process firstly before encapsulation to improve the sensitivity of the sensor. Based on the finite element thermal analysis, it is found the designed temperature compensation diaphragm's maximum strain is about 0.073 με when the temperature is increased from -10 ℃ to 50 ℃, which demonstrates the thermal expansion coefficient mismatch has less influence on the diaphragm and this system has high temperature reliability. Besides, sensing accuracy of the fiber sensor is improved by the design of cantilever structure, which makes the sensing immune to the complex environment. We fit and revise the results of joint compensation between temperature compensated diaphragm and the strain sensing diaphragm by the origin. The results show that the sensing linearity can reach more than 0.9999, and the full range accuracy is about 0.05%.