This paper researches a three-dimensional positioning scheme for emergency rescue of trapped firefighters at the fire scene. This scheme adopts Chirp Spread Spectrum(CSS) and it's particular Symmetric Double-Sided Two-Way Ranging(SDS-TWR). Combining BMP085 pressure sensor to measure altitude, it can implement three-dimensional positioning of firefighters. Due to the complex environment of the fire scene would cause multipath effect when Chirp signal being transmitted, this scheme uses Kalman filtering method to filter out mutative coordinate value, thus the positioning error can be controlled within 1 m.