A grand piano soundboard with a bar and sound tunnels has an outer wall with first and second grooves. The first groove is arranged diagonally in the width direction. The second groove is arranged diagonally in the length direction. The grooves cross and connect on the outer wall of the soundboard. The outer wall is divided into four resonance regions, and its center has a bar assembly having strip-shaped bar members arranged on both sides of the grooves in pairs; The grooves form a sound tunnel on the outer wall. The soundboard is changed from the previous free vibration mode to the current standard vibration mode. The treble of the grand piano is bright and the bass was sonorous and mellow from the perspectives of vibration, resonance and phonation. The design scheme has outstanding substantive characteristics and remarkable technical progress, and has obtained technical results.