In line with the original cost reducing and benefit increasing principles for offshore oil field facilities, wellhead platform was newly built near the existed production platform in Bohai Q oil field and the overall density increasing was carried out in the original dense well network, the operation difficulty increased rapidly. By means of the old borehole data processing, new well trajectory design optimization, anti-collision trajectory design and anti-collision monitoring, hole trajectory precision guidance technology for dense cross well network is developed. By the successful application of this technology, the work efficiency is improved, which effectively ensures the smooth implementation of well trajectory density increasing in dense cross well network of old oil field and reduces the collision risk.