We propose and analyze the fast wireless anti-collision algorithm(Improved Bit-by-bit Binary-Tree algorithm(IBBT)) in Ubiquitous ID system. We mathematically compare the performance of the proposed algorithm with that of Binary Search algorithm(BS), Slotted Binary-Tree algorithm(SBT) using time slot, and Bit-by-bit Binary-Tree algorithm(BBT). We also validated analytic results using simulation. According to the analytical result, comparing IBBT with BBT which is the best of existing algorithms, the performance of IBBT is about 304% higher when the number of the tags is 20, and 839% higher for 200 tags.