To solve the problem that the fingerprint database updating requires a huge amount of time and laboring effort, a new Received Signal Strength (RSS) estimation method was proposed in WiFi environment. Part of remeasured RSS fingerprints was used to fit RSS surface by the radial basis function interpolation, the RSSs of the unknown reference points were estimated nearby the known reference points, and then the whole fingerprint database was update. The extensive experiments prove that only a quarter of the reference points need to be remeasured, the cumulative error probability will be similar with the actual database within the positioning error of 2 m, and thus the method guarantees the satisfactory positioning accuracy.