The invention relates to environmental-friendly diamond grinding liquid and a preparation process thereof. The environmental-friendly diamond grinding liquid is characterized by being prepared from the following components in percent by weight: 0.1-20wt% of grinding material, 60-99wt% of solvent, 1-20wt% of emulsifying agent, 1-20wt% of thickening agent and 1-20wt% of suspending agent, wherein thegrinding material contains at least one of polycrystalline diamond micropowder, polycrystalline-like diamond micropowder and monocrystalline diamond micropowder; the solvent contains at least one ofnaphtha, white oil, alkylbenzene and isoparaffin; the emulsifying agent contains at least one of an alkylphenol-series emulsifying agent, a benzenesulfonic-acid-series emulsifying agent, a polyoxyethylene-ether-series emulsifying agent and a sorbitol-series emulsifying agent; the thickening agent contains at least one of olefins polymer and silicon-alkane polymer; the suspending agent contains atleast one of paraffin series, epoxy resin, C9 petroleum resin and butadiene styrene rubber SBS. The environmental-friendly diamond grinding liquid is prepared by the steps of dissolving, stirring, dispersing, coating, emulsifying, disaggregating, reverse treatment, cooling and converting. The environmental-friendly diamond grinding liquid has the advantages of wide working-temperature range, longstability time and stable-controllable grinding speed and the like.