In view of the shortcomings of existing oil-water interface detection device, i.e., low accuracy, and short lifetime and large maintence for mechanical parts, a float type oil-water interface detector was designed.The oil-water interface detector uses a gravity sensor as measurement element, transferring gravity signal into voltage signal.Then, by using 4～20 mA two-wire U/I transmitter XTR101, apractical transmission circuit was designed, which converts the voltage signal into current signal.Finally, through the single-chip MSP430 F149 monitoring and control device, real-time display of oil-water interface level, along with oil-water interface alarm and automatic drainage function, was realiezed.Experiments show that the floating oil-water interface detector has good anti-interference ability, stability and reliability, with the average error within±3%.