Spatial structure of the D-type knotter was studied based on its working sequence. Key spatial parameter relationships were confirmed to ensure the eight knotting processes going well through analyzing the knotter working principle, and the parameter model of knotter was build. Key spatial axes parameters were also designed by using mathematica 8.0 software, and two knotter frames were finally determined with different spatial parameters. The knotting experiments were carried out by using the two different knotter frames which were both assembled with the homogeneous New Holland parts, the results showed that, in the indoor experiment, the knotting rate of knotter frame Ⅰ (KFI) was 1.0% lower than knotter frame Ⅱ (KFII), while the average breaking force of the knot formed by the KFI was 13.9% higher than KFII at the same preload. In the field experiment, the knotting rate of KFI was decreased 4.0% in compared with KFII while its average breaking force was 2.5% higher than KFII. The average breaking force of the knot formed in the field was 94.2%~115.9% higher than indoor due to the different preloads and the additional extend force of the compressed straw baler. 