Abstract: To address the problem that traditional location fingerprint matching algorithm can only represent the characteristics of single dimensional fingerprint points, an indoor locating method based on smartphone's received signal strength (RSS) fingerprint was proposed. In this methods richer fingerprint point information was extracted by data collection, feature extraction and access point (AP) weight assignment in the offline phase, and the improved K nearest neighbor (KNN) algorithm was used to match the test Point with the fingerprint Point in the online phase. In addition, a Bluetooth sensor was used for experimental verification on a smartphone with Android 10 as the operating system version, and 30 test points were randomly selected. Two conclusions can be drawn from the experiment. First, the four-way RSS fingerprint is better than the traditional one-way RSS fingerprint. Under the same experimental conditions, the four-way RSS fingerprint can reduce the positioning error by up to 13.4%. The second is the algorithm proposed by combining the four-way RSS fingerprint, with an average positioning error of about 1.61 meters and a response time of milliseconds.