The high Q-factor coil with negative impedance converter (NIC) is investigated. The NIC leads to the enhanced transmission efficiency at a long distance for wireless power transfer (WPT) with magnetic resonance coupling method. The negative resistance generated by the NIC reduces the resistance of the coil. The coils were considered for the practical application such as effects of the ferrite and conductor. The transmitter (TX coil) is presented 250 mm by 250 mm with thickness of 0.9 mm, and has the impedance of 20+j1480 Ohm and the Q-factor of 76. The Q-factor of the TX coil was enhanced from 76 to 1640 due to the negative resistance of 15 Ohm, which was about 21 times higher than that of the conventional one. The power transmission efficiency (PTE) was measured with respect to the transmission distance between the TX and RX coils. The PTE of the system was 29% at a distance of 300 mm. This result shows that the PTE was greatly improved at a long distance when the NIC was applied.