Silicate bacteria or Bacillus mucilaginosus, which is a special Bacillus species producing a rich variety of exo-polysaccharides and have some capability of dissolving potassium, phosphorus and silicate from minerals, may have wide potential uses in agriculture and industry. In order to increase its capability on hydrolyzing phytate phosphorus so as to make a microbial fertilizer, a transgenic Bacillus strain highly secreting phytase was constructed by the particle bombardment method using a phytase secreting expression vector pSP43 with a mini-tn5 transposon and a phytase expression cassette. In this study, the vector pSP43 was triumphantly transferred into the Bacillus mucilaginosus, and three transgenic strains with a stable copy of phytase expression cassette integrated into the chromosomal of the Bacillus mucilaginosus by tn5 transposition were selected. The phytase activity of engineering strains obtained increased 36-46times in comparison with the start strain D4B1. This is the first report made a transgenic Bacillus strain by the particle bombardment method successfully.