For the large angle drilling construction with hole depth greater than 300m, the construction difficulty increases obviously. By improving construction chamber design in the tunnel, the smooth drilling construction and the safety are ensured. Based on the improvement of equipment selection and installation, hole structure, drilling parameters, flushing medium configuration, common accidents and the prevention, the construction technology of large apex angle drilling in tunnel is summarized, the drilling construction of borehole with apex angle 56 degree and designed depth 593m has been completed.