Bulk tungsten and tungsten transmission electron microscopy (TEM) lamella are implanted with 15 keV helium ions at about 873 K to study the microstructure evolution. The samples are implanted to about 11017 He+/cm2. The projected range of the helium ion in tungsten is about 43.9 nm, calculated with the stopping and range of ions in matter program (the SRIM code). The density of pores with diameters ranging from 90 nm to 430 nm is detected on the surface of helium implanted bulk tungsten by field emission scanning electron microscopy. Blistering is also observed on the surface of helium implanted bulk tungsten. The TEM results indicate that fuzz microstructure is formed in helium implanted tungsten TEM lamella, and stacking faults and micro-pores are observed in the fuzz structure. Besides, the density of nano-scaled helium bubbles is detected around the mirco-pores.