In this paper, the release of model drug aspirin (ASP) from biodegradable polyesterurethane networks was studied. Poly(D,L-lactide-co-glycolide)urethane (PULG) networks were prepared from hydroxyl telechelic star-shaped oligo(D,L-lactide-co-glycolide) coupled with 1,6-diisocyanate-2,2,4-trimethylhexane and 1,6-diisocyanate-2,4,4-trimethylhexane or isophorone diisocyanate. PULG networks turned from transparent to opaque after ASP loading. PULG networks with lower crosslinking density always resulted in higher drug loaded content. The results of differential scanning calorimetry (DSC) and scanning electron microscope (SEM) measurements demonstrated that ASP was uniformly distributed in the networks. The drug release courses of ASP from PULG networks in phosphate buffered saline pH = 7.0 at 37 °C could be divided into three stages. Firstly, ASP release was at approximately uniform rate from PULG networks; Secondly, the release rate obviously increased for the degradation of the PULG networks; Thirdly, the release rate decreased gradually because most of the ASP had diffused out of the PULG networks. The crosslinking density of polyesterurethane networks also affected drug release rate. The in vitro release test revealed that ASP accelerated the degradation process of PULG, which exhibited a typical erosion-controlled release mechanism.