To evaluate the limit transmitting detonation distance (i.e. maximum transmitting detonation distance at a confidence level of 0.95 and reliability of 0.999) in the air of bi-directional booster used in oil and gas wells, a transmitting detonation test of bi-directional booster was performed by the mathematical statistic method-up-and-down method commonly adopted in sensitivity test of pyrotechnics. The numerical simulation of transmitting detonation mechanism and explosion process for bi-directional booster was carried out by LS-DYNA software. Results show that the maximum transmitting detonation distance with reliability of 0.999 under a confidence level of 0.95 in the air of bi-directional booster is 82.8 mm. The numerical simulation results support the experimental one of about 82.8 mm in a certain extent.