Disclosed is a paddy field straw mulching rice drill seeder. The paddy field straw mulching rice drill seeder is characterized in that a paddy field straw mulching cutter shaft (19) is driven by an intermediate drive gear box (7) to rotate, and then rotates a paddy field straw mulching cutter (4), and when rotation speed of a tractor rear land axle (1) is responded on a rotation speed sensor (2), the rotation speed sensor (2) provides rotation speed signals to a control box (8) through a sensing connection line (3), the control box (8) adjusts rotation speed of a stepping deceleration motor (11) through a motor line (9), a motor shaft (13) starts rotating, and drives a small gear (12) to rotate, and then due to the fact that a large gear and the small gear (12) are meshed with each other, the large gear is driven to rotate, a sowing axle (14) rotates so as to enable a seed sowing device (16) to start working, the seed sowing device (16) evenly discharges seeds in a seed box (10), the seeds fall in a seed conveying pipe (18), the falling seeds are sown on the surface of a field after being ploughed in drill, and then wheat straw mulching, land formation and rice drill sowing work can be completed once, and synchronization of sowing speed and tractor forwarding speed can be achieved.