In view of poor film-forming stability and short-term protection of the conventional inhibitors in strong acidic medium, a microemulsion inhibitor（HSL-1）for coiled tubing was prepared by means of the liquid droplet and the quasi three-element-phase diagram method with employing dodecyl-trimethyl-ammonium bromide （DTAB）, hexadecyl-trimethyl-ammonium bromide （CTAB）, Mannich base, butanol and mineral oil as raw materials. The effects of HSL-1 mass fraction，acid mass fraction and environmental temperature on corrosion inhibition performance were investigated by using the static weight-loss method. The inhibition property and mechanism of HSL-1 for coiled tubing were also analyzed by virtue of the scanning electron microscope (SEM) and polarization electrical resistance measurement. The results showed that HSL-1 is a mixed type of inhibitor to inhibit the cathodic process and microemulsion with size of 15nm~85nm possesses an O/W structure; the inhibition of HLS-1 for coiled tubing under downhole condition is better in acidic medium when the HSL-1 mass fraction is in the range of 1.0~2.0 % and the corrosion rate is less than 3~5 g/ (m2·h). At the same time, the release rate of the active components can be controlled by the O/W structure of microemulsion and the effective mass fraction of inhibitor in the flow-back fluid was maintained, still keeping very low corrosion rate of 0.381 g/(m2·h) after the CT80 coupon immersed 12h in spent acid and the long-term inhibition for coiled tubing can be obtained.