Catamaran vessels have been used for various purposes such as leisure craft and research vessel. Especially, asymmetric catamaran has a half of the symmetrical hull and flat side of facing inward demi-hull, and has feature of planing hulls such as hard chine, spray rail. Therefore, these vessels can travel at high speed with better stability and resistance performance. However, these features cause asymmetric catamaran to have large trim angle at high-speed condition, which cause problem on vessel's operation performances such as visibility and dynamic instability motion. To overcome these negative effects, tunnel shape in stern has been introduced. By applying this shape, trim angles are also suppressed because large dynamic lift developed on the exit region of tunnel stern. In this research, tunnel stern was applied on the asymmetric high-speed catamaran to evaluate vessel's hydrodynamic performance by numerical method, and the tunnel stern types are distinguished by slope of tunnel exit region: flat or narrow types. Consequently, it is confirmed that the total resistance of tunnel types is lower about 1.6～5.0% than the bare hull in the wide speed range while showing almost same phase with the bare hull after FnV=2.3. Also, narrow type improves resistance performance further than flat type. On the other hand, trim angles show different trend with each tunnel type. In case of narrow type, the trim angle is stabilized after FnV=1.8 while that of flat type show an increasing trend as ship speed increase. These indicated that the narrow type has better resistance and operation performance than others.
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