The invention relates to low-melting point and lead-free microcrystalline glass for closure of high temperature electrothermal tube and a process for preparation thereof. The compositions of the microcrystalline glass are Bi2O3-SiO2-B2O3-Al2O3-CaO. The weight percentages of the oxidizing substance of every composition are that Bi2O3 takes 20-70%, SiO2 takes 10-30%, B2O3 takes 1-15%, Al2O3 takes 5-30%, CaO takes 1-30%, ZrO2 takes 1-10%, TiO2 takes 1-10% and ZnO takes 1-10%. The process for preparation is that weigh Bi2O3, SiO2, Al2O3 and the like according to the weight percentage and mix sufficiently, the mixture is melted for 1-6 hours at a temperature of 1200 DEG C-1600 DEG C, then the mixture is water quenched, cooled, solidified and ball grinded to microcrystalline glass powder, after pelleting, modeling and dumping, the microcrystalline glass powder can be used for vacuum seal for every high temperature electrothermal tube at a temperature of 800 DEG C-900 DEG C. The invention has good wear-resistance and corrosion resistance, high strength, has no environmental pollution component, can directly realize nontoxic and pollution-free seal with the high temperature electrothermal tube, and has wide application.