Natural enzymes have been widely used in industrial catalysis due to the superior selectivity and high efficiency. However, the loss of activity and separation of products are two significant obstacles to overcome. Here, temperature-sensitive single horseradish peroxidase(HRP) nanogels were prepared by aqueous in-situ polymerization. TEM suggests that a single HRP was caged in one poly(N-isopropylacrylamide) nanoparticle. The enzymatic reaction below 32 centigrade was performed homogeneously and the caged HRP exhibited the same catalytic behavior as its native counterpart. The recovery of the HRP nanogels from the reaction was achieved via raising temperature above 32 centigrade, while the enzyme activity was recovered when the nanogels were dissolved below 32 centigrade. The stability and ease of recycle make SMART single-enzyme nanogels promising for various applications, particularly in large scale industrial biocatalysis where the running cost is of concern.