Any monitoring must first clarify the objective and its monitoring characteristics. The two important characteristics of microseismic are: tiny, and rupture with mainly shear dislocation mechanism. The monitoring characteristics obtained by the features are: often the signal-to-noise ratio (S/N) is <1 from a few hundred meters away, and the traditional location fails; One hypocenter radiates longitudinal and transverse waves into space, and the amplitude and polarity of the waves change with different directions. This is the essence or first principle of microseismic monitoring. Based on this, it is found that many people: (1) adhere to the traditional relocation with S/N>1, such as costly proximity monitoring, or continuously but effectively-limited denoising, or helplessness; But cannot coexist with residual noise after effective denoise, extract microseismic information through data migration and stacking (DMS); (2) have used DMS, but the seismic wave vectors are not (correctly) extracted from the 3-C records by using the far-field displacement solution generated by the shear couple source, especially the direct transverse or rotation wave vectors SV and SH with large amplitude, slow attenuation, and long propagation; And (3) The amplitude and polarity of the arrival seismic wave are not considered to be a function of the direction of the incoming earthquake; That is, the focal mechanism of passive or natural earthquakes, the stress-strain constitutive relationship in elastic mechanics, and the Anderson discussion in structural geology or rock mechanics are not used to guide the DMS and explanation of microseismicity. These problems are evident in many detections of surface, well, mine safety, inversion for velocity models, and micro/small earthquake precursors before destructive earthquakes. This paper takes VS (Vector Stacking) R D as example to illustrate how to solve the above problems using the first principle; and in order to ensure reliable microseismic monitoring in the sense of high probability, many necessary conditions should be strictly followed.