A novel method for fabricating thermo-regulating alginate fiber by wet spinning from phase change material (PCM) microemulsions was proposed and carried out. In order to synthesize the PCM microemulsion successfully, different emulsifiers (alkylphenol polyoxyethylene ether (OP-10), sodium dodecyl sulfate (SDS) and their mixture) were added into the stock solution system. The solution systems with emulsifiers were observed under optical microscope and evaluated by using a differential scanning calorimeter (DSC); the results showed that only the solution system with the mixture of OP-10 and SDS transformed into PCM microemulsion, corresponding to the success of fiber formation by wet spinning. In addition, the microemulsion had a stable thermal property based on the DSC result, in which the latent heat capacity remained at 97.3% after 100 cycles of heating and cooling. The thermo-regulating alginate fiber was evaluated in terms of morphology, thermogravimetric (TG) analysis and differential scanning calorimetry. The results showed that the fiber had a smooth surface and porous structure in the cross-section, the bimodal TG curve of alginate fiber indicated that the PCM was successfully embedded into fiber and the DSC results demonstrated that the thermo-regulating alginate fiber had a comfortable phase change temperature of 25–35℃, and an acceptable phase change enthalpy of about 20 J/g.