When femtocells are deployed intensively in Long Term Evolution (LTE) systems, there would be strong interference between femtocells. Concerning downlink interference of femtocell, an adaptive power control algorithm based on pathloss was proposed. According to the threshold of Signal to Interference plus Noise Ratio (SINR), the user of femtocell was given the adjustment flags and then the flags were sent to femtocell through uplink channel. According to the pathloss and allocated resources block of the user, femtocell adaptively adjusted the transmission power for the purpose of controlling SINR of the user on the basis of adjustment flags received. The simulated results show that the algorithm is better at controlling the SINR of femtocell users and improves the average throughput of femtocell with 1.7Mbps at least compared with the situation of no power control. At the same time, it indicates that the more dense of femtocell, the more apparent of control effect.