The self-assembly behavior of collagen under the regulation of the external environment is important for the construction of collagen-based materials. In this study, the effects of temperature, pH, and ion concentration on the self-assembly property, microrheology, and microstructure of acid-soluble collagen (ASC) extracted from lamb skin were investigated. The kinetics of ASC self-assembly under different environmental conditions was captured by monitoring the turbidity over time. The results showed that the ASC assembly process was accelerated by temperature increase in the range of 25–37 °C, and the self-assembly was unfavorable when the temperature exceeded 37 °C. The pH closed to the isoelectric point of ASC was conducive to assembly, and appropriate ion concentration increased the assembly rate of ASC. The microrheology reflected the influence of environmental conditions on the assembly process through the changes in the elastic and solid-liquid transition points of the solution system, and the results were consistent with the conventional turbidimetry method. Scanning electron microscopy showed that ASC formed fibril structures with different diameters in different environments. In addition, infrared spectroscopy showed the changes of secondary structure of ASC during the assembly process. The amino acid composition, UV spectrum, secondary structure, and morphology of ASC were characterized. The above results provide a foundation for the construction of controllable ASC self-assemblies from lambskins.