Generation of ultraslow solitons and dynamic behaviors of soliton pairs with low intensity input pulse in semiconductor asymmetrical quantum wells (QWs) are investigated. It shows that the QWs structure can provide giant Kerr-type nonlinearity via resonant tunneling, therefore the group velocity dispersion can be balanced, which results in the generation of the ultraslow solitons and soliton pairs, and the initial relative phase of the soliton pairs plays an important role in the propagation of soliton pairs in such a semiconductor QW system. These properties are very useful in practical applications, such as quantum information processing and optical buffers.