This paper introduces the principle of precision delay circuit of linear ramp - wave generator, which is used in digital programmable precision delay unit. A precision delay circuit, which uses AD9501 as its core component, has been designed, and a fully reset circuit of AD9501 is designed also. The frequency of this circuit can be up to 10ps. The result of experiment indicates this data collecting system has high precision and can collect high frequency geologic radar echoed signal of 30Hz using equivalent sampling technology. This system is very important theoretical and practical significance in the measurement and control field.