Tri-ridged PDC cutter is widely used at drilling sites in oil, gas, geothermal, and other fields. Compared with the conventional PDC bit, the PDC bit combined with the conventional PDC cutter and tri-ridged PDC cutter can effectively improve the rate of penetration. The article conducts a laboratory experiment on cutting granite with a single tri-ridged PDC cutter. An analysis of the rock-breaking law of the tri-ridged PDC cutter is conducted at various cutting angles and cutting depths. The experimental results provided insights into the cutting force, particle size distribution of cuttings, and the variation in mechanical specific energy of the tri-ridged PDC cutter. A high-speed camera system is used to observe the cutting process of a tri-ridged PDC cutter on granite, and the rock-breaking advantages of a tri-ridged PDC cutter are explained. The results show that the cutting force of the tri-ridged PDC cutter increases linearly with the cutting depth and the cutting angle. The average cutting force is 13.89% lower than that of the conventional PDC cutter. Majority of the overall mass consists of large-particle size and small-particle size cuttings, accounting for over 80% on average. The tri-ridged PDC cutter exhibits the lowest mechanical specific energy when used with a cutting angle of 15°–20° and a cutting depth of 2–2.5 mm. Observed by high-speed camera system, due to the stress concentration effect of the lower convex edges, the area under the cutter is more likely to be damaged. The side-cutting surface of the tri-ridged PDC cutter can inhibit the accumulation of rock chips, which leads to better impact resistance for the tri-ridged PDC cutter. The properties and operating parameters of tri-ridged PDC cutters can be used to guide the design of conventional PDC cutters and tri-ridged PDC cutters with mixed distribution PDC bits.