A design method for coefficient-adjustable FBG strain sensors was given out to deal with the problem of the limited scale or precision for a Fiber Bragg Grating(FBG) strain monitor. Theoretical and experimental researches were performed to test the characters of the sensors on long-gauge or high precision,then two kinds of high qualified FBG strain sensors(slice mode and FRG packaging mode) were developed and fabricated to validate the design. The sensitivity coefficient of each sensor was analyzed,and it was also calibrated by experiments. Finally, the errors between theoretical and experimental sensitivity coefficients were analyzed. Experimental results indicate that the ranges of the long-gauge sensors have increased by 243% and 126%, and the accuracies of the high-precision sensors have reached 0.51 με and 0.52 με,respectively. In the experiments of calibrations,both kinds of sensors show good linearity and repeatability,and the correlation coefficient is up to 0.999.