This paper proposes an efficient bandwidth allocation scheme to fully utilize the multi-access ability of multimode terminals in heterogeneous networks. To model the fact that the suitability of different networks to different traffics varies, which is seldom considered in previous literature, the term "Match-Degree" is introduced and calculated using grey relational analysis. Afterwards, two methods, namely weighted bandwidth factor and cumulative utility function are proposed to integrate the influence of "Match-Degree" into the conventional utility-functions. Moreover, energy consumption and network price are also considered to make our model more comprehensive. The bandwidth allocation problem is formulated as maximizing the overall utility by adjusting the bandwidth allocated to each user. Based on optimization theory, an iterative algorithm is constructed to solve this problem. And numerical results validate the performance enhancement of our scheme compared with the existing ones.