The utility model relates to an online optical detection sensing device in transformer substation air switch position, shelter from the device including light detection device with light, light detection device includes the black plate body, the smooth input channel and light output channel of two rectangular shape round holes that parallel are seted up to the inside of plate body, light input channel is located same horizontal plane with light output channel's bottom, and has the light transmissivity between the two, be equipped with optical input optic fibre in the light input channel, be equipped with light yield optic fibre in the light output channel, light input channel and light output channel's bottom inclines to be equipped with a level crossing respectively relatively to light that the messenger was got into by light input channel is jetted out by light output channel through level crossing reflection back, light shelters from the device for block the light transmission between light input channel and the light output channel. The utility model provides high substation operation fail safe nature with detect intelligent level, the maloperation of personnel's back brake is patrolled and examined in effective prevention, has reduced and has patrolled and examined operation maintenance cost reduction.