Abstract: Dynamic observation of dissolving-crystallization process of NaCl crystal and in-situ reaction of BiVO₄ crystal were carried out by using an environmental scanning electron microscope(ESEM) and the micro-manipulator/micro-injector system(MMI/MIS).The step precision of MMI system in three directions,retreat-forward linearity(Z-axis),clock-unclockwise rotation(X-axis) and up-down rotation(Y-axis) are 5,5 and 0.5 nm,respectively.The size of the liquid droplet of MIS system was about 200 μm-300 μm.The influences of the water wetting environment on dissolving,growth and growing rate of crystals were studied by changing pressures(450-850 Pa) in chamber and sample temperatures(0-50 ℃),as well as by controlling states of water evaporation and condensation.Reactive products of BiVO₄!octahedron were obtained at 700 Pa and 4 ℃ via liquid micro-injection approach by using two MMI/MIS systems,i.e.,one for NH₄VO₃ and one for Bi(NO₃)₃ injection.