Active queue management (AQM) is a very active research area in networking. Compared with drop-tail, AQM can provide smaller average queue delay and higher bandwidth utilization. Although the performance of proportional integral (PI) controller is superior to that of random early detection (RED), its convergence speed is slow. This paper proposes an adaptive proportional integral (API) algorithm based on the original PI. API obtains load information by measuring the current packet-dropping rate, then sets PI parameters accordingly. Verified by using NS-2 simulations, API can achieve faster convergence speed and smaller queue oscillation than PI and PIP (proportional integral based series compensation and position feedback compensation) which is an improved algorithm of PI.