The stress measurement of deep soft rock mass is very hard; and the existing testing technique is not available. Thus

a 3D compressive sensor is particularly invented to measure the geostress of soft rock mass; the corresponding method of calculation is introduced; the calibration test

interference test and laboratory model experiment for the sensor are also performed. The calibration test data show that the static properties

such as linearity

repeatability

etc.

are well. As the load increases gradually

the measuring error of sensor is diminishing

until zero

and then increasing

but less than 10% as a whole; so a conclusion is obtained that the stress within a reasonable range can be perceived accurately. The interference test shows that the mutual disturbance of three perception surfaces is negligible. The laboratory model experiment data show that

when forcing repeatedly

the value detected by the sensor approach to the load application more and more

almost equal finally

and further summing-up is gained that the 3D compressive sensor basically meet engineering practice requirements. In addition

the optimization design of the sensor is discussed preliminarily.