In order to study the characteristics of rock mass， karst development， ground stress and groundwater in the tunnel of the Dadu River to the Min River Replenishment Project， 8 horizontal boreholes with a total of 2300 m were arranged in the diversion route of the Luding Water intake Middle route scheme. In order to meet the demand of horizontal hole comprehensive testing， a set of storage comprehensive logging instrument suitable for horizontal drilling is developed. This paper analyzes the basic working principle of the horizontal hole multi-parameter comprehensive measuring instrument. The circuit composition selection of each functional unit is described in detail. DSP microprocessor and large-scale integrated circuit are mainly used， and the sensor technology is combined to realize the comprehensive measurement of many parameters， including： pressure， temperature， natural gamma ray， acoustic wave velocity， and TV image in the hole. Integrated testing instrument integrates analog sensor， analog conditioning circuit， data acquisition， data processing， information storage， data communication， information exchange， measurement and control hardware and software， computer display and other functions， is an indispensable technology for horizontal hole comprehensive testing. It has been successfully applied in the horizontal directional hole of the Dadu River to the Min River Replenishment Project， and the problems of incline， azimuth， pressure， temperature， natural gamma ray and TV test in the hole have been solved in one trip， thus ensuring the safety of the hole and reducing the labor intensity as far as possible.