The alpine valley region in southwest China is the key area where Chinese major railway projects are planned such as Sichuan-Tibet Railway. However， most tunnel works designed in the alpine valley region has the characters of deep burial and great length， and conventional vertical drilling methods cannot satisfy the sophisticated investigation requirements. This paper puts forwards horizontal directional investigution technology， by which horizontal directional holes can be designed along the tunnel axis to provide an effective method for tunnel investigution. The key components of directional investigution technology includes drilling technology， coring technology， drilling trajectory control technology， MWD / LWD， comprehensive logging technology. The existing problems are examined with analysis of the development and application status of horizontal directional investigution technology at home and abroad， and it is proposed to develop a safe， efficient， economical and reasonable horizontal directional investigution technology system through R & D on key technology and equipment for horizontal directional multi-process drilling with capacity over 3000m in a single trip.