Low density spreading code division multiple access (LDS-CDMA) is a newly emerging multiple access technique with its potential to support massive connectivity. However, the existing LDS-CDMA has the drawback of high multiuser detection complexity and does not take full advantage of the channel state information. To tackle these problems, a novel low-complexity multiuser detection scheme based on dynamic factor graph is proposed with the aid of a preset threshold V_th. For the proposed scheme, a good tradeoff between computational complexity and bit error rate (BER) performance is determined by V_th. Moveover, a V_th setting method is given, according to the average effective function node degree E (d_k,j). Simulation results show that the proposed scheme has a substantially reduced computational complexity with negligible BER performance losses, compared to the original MPA-based scheme.