As a special kind of grinding, honing is a typical low speed precision machining process, which is of low grinding speed, little grinding heat and little thermal-residual deformation of workpiece, suitable for precision machining of holes in the precision couples of internal-combustion engine. Experimental investigation on effects of process parameters on honing efficiency of small holes was put forward in this paper to obtain economical machining efficiency. Circumferential speed, reciprocate speed and working pressure of honing stone are the key factors which affect the machining efficiency and quality of honing. Taking it as a case study the honing of the small middle hole of the valve seat of balancing valve couples of internal combustion engines, honing experiments were carried out in this paper to investigate the relationships of material removing rate in rough honing versus circumferential speed, reciprocate speed and working pressure in honing of small holes. The results show that in honing of small holes the material removal rate in rough honing increases with circumferential speed, reciprocate speed and reticulate cross-angle increasing but decreases when the two speeds exceed certain critical values, and the surface quality in finishing honing is improved by increasing circumferential speed.