Embodiments of the present invention disclose a pilot signal transmitting method, and a channel estimation method, an apparatus, and a system. The method includes: within a transmission time interval (TTI), transmitting a first pilot signal (CPICH1) on a first antenna, and transmitting a second pilot signal (CPICH2) on a second antenna; when no first-type terminal is scheduled within coverage of a MIMO system within the TTI, transmitting a third pilot signal (CPICH3) on a third antenna, and transmitting a fourth pilot signal (CPICH4) on a fourth antenna; and when a first-type terminal is scheduled within the coverage of the MIMO system within the TTI, transmitting the CPICH3 and a fifth pilot signal (CPICH5) on the third antenna, and transmitting the CPICH4 and a sixth pilot signal (CPICH6) on the fourth antenna. By using the method, interference of a pilot signal to a legacy terminal can be greatly reduced.