An ultrasound system, comprising: an ultrasound data acquisition unit configured to transmit ultrasound signals to a target object via a probe, form ultrasound data corresponding to the target object based on ultrasound echo signals received from the target object; Characterized in that the system also comprises: a storage unit for storing a three-dimensional color reference table for providing colors corresponding to at least one of intensity accumulation values and shading values throughout depth; and a processing unit configured to form volume data based on the ultrasound data formed from the ultrasound data acquisition unit, characterized in that the processing unit is configured to perform ray-casting for emitting virtual rays on the volume data, calculate intensity accumulation values by accumulating intensity values of sample points on each of the virtual rays, calculate depth accumulation values by accumulating depth values of the sample points on each of the virtual rays, form a depth information image based on the depth accumulation values, calculate surface normals corresponding to pixels of the depth information image, calculate scalar product values between vectors of the surface normals and vectors of the virtual rays as shading values, retrieve the three-dimensional color reference table to extract the colors corresponding to the intensity accumulation values and the shading values, and apply the extracted colors to the volume data to form a three-dimensional ultrasound image. an ultrasound data acquisition unit configured to transmit ultrasound signals to a target object via a probe, form ultrasound data corresponding to the target object based on ultrasound echo signals received from the target object; Characterized in that the system also comprises: a storage unit for storing a three-dimensional color reference table for providing colors corresponding to at least one of intensity accumulation values and shading values throughout depth; and a processing unit configured to form volume data based on the ultrasound data formed from the ultrasound data acquisition unit, characterized in that the processing unit is configured to perform ray-casting for emitting virtual rays on the volume data, calculate intensity accumulation values by accumulating intensity values of sample points on each of the virtual rays, calculate depth accumulation values by accumulating depth values of the sample points on each of the virtual rays, form a depth information image based on the depth accumulation values, calculate surface normals corresponding to pixels of the depth information image, calculate scalar product values between vectors of the surface normals and vectors of the virtual rays as shading values, retrieve the three-dimensional color reference table to extract the colors corresponding to the intensity accumulation values and the shading values, and apply the extracted colors to the volume data to form a three-dimensional ultrasound image. a storage unit for storing a three-dimensional color reference table for providing colors corresponding to at least one of intensity accumulation values and shading values throughout depth; and a processing unit configured to form volume data based on the ultrasound data formed from the ultrasound data acquisition unit, characterized in that the processing unit is configured to perform ray-casting for emitting virtual rays on the volume data, calculate intensity accumulation values by accumulating intensity values of sample points on each of the virtual rays, calculate depth accumulation values by accumulating depth values of the sample points on each of the virtual rays, form a depth information image based on the depth accumulation values, calculate surface normals corresponding to pixels of the depth information image, calculate scalar product values between vectors of the surface normals and vectors of the virtual rays as shading values, retrieve the three-dimensional color reference table to extract the colors corresponding to the intensity accumulation values and the shading values, and apply the extracted colors to the volume data to form a three-dimensional ultrasound image.