Objective To investigate the mycelia growth of the mutant strain Paecilomyces bainier sp229-7 and it's biotransformation from ginsenoside Rb1 to Rd. Methods The substrate was biotransformed by the mutant in different conditions, and the products were analyzed by HPLC. Results The period of vigorous growth of the mutant was 12-48 h. The optimal transformation temperature range was from 27 ℃ to 32 ℃. The best time for adding substrate was 36 h after inoculation and the substrate (Rb1 20 mg/mL) was specifically transformed into ginsenoside Rd. The transformation process was terminated at 72 h. The ginsenoside Rb1 could be transformed to Rd by all of mycelia, crude enzymes and external enzymes. Conclusions Compared with the reference, the mutant of Paecilomyces bainier sp229-7 growth is quicker and the transformation efficiency has been greatly improved. The reaction time can be shortened to 3 days, and the amount of substrate increased at least 20 times.