This paper presents a new simulation method for modeling and simulation of high-density integrated optical circuits based on high index contrast (HIC) waveguides with complex topology. The method combines the time-domain reflective beam propagation method (TD-RBPM) and the slow-wave finite-difference time-domain method and is hence referred to as the time-domain hybrid BPM (TD-HBPM). It is capable of handling arbitrary optical integrated circuits with perpendicularly located input and output ports. The application to the two HIC optical circuits shows the accuracy and efficiency of this method.