Objective: To determine the expression of non-muscle myosin heavy chain 9(MYH9) in osteosarcoma and its effect on the migration and invasion abilities of tumor cell. Methods: A total of 65 cases of osteosarcoma and 20 cases with benign osteochondroma who underwent resection operation in the Orthopaedics Department of our hospital from January 1st 2009 to January 1st 2015 were selected. Their mR NA levels of MYH9 were tested by q rt-PCR. Immunohistochemical method was used to examine the expression of MYH9 in osteosarcoma and the correlation between the positive expression of MYH9 and the clinicopathological features of patients was illustrated by statistical analysis. MYH9 was compounded artificially. The expression of MYH9 in SAOS2 osteosarcoma cells was decreased by si RNA. Scratch test was used to determine the change of SAOS2 cell migration ability after MYH9 silence. Transwell assay was employed to detect the change of cell invasion ability after MYH9 silence.Results: The expression levels of m RNA of MYH9 and protein in osteosarcoma tissues were significant higher than those in benign osteochondroma tissues. The high expression of MYH9 in osteosarcoma tissues was apparently related to the high Enneking classification(III classification) and lung metastasis. SiR NA of MYH9 could evidently decrease the expression level of MYH9 in SAOS2. The down-regulated expression of MYH9 could inhibit the migration and invasion abilities of SAOS2 cells. Conclusions: MYH9 shows a trend of high expression in osteosarcoma tissues, and its high expression is associated with features such as tumor invasion and metastasis. The down-regulated MYH9 can realize an anti-tumor effect by inhibiting the migration and invasion of osteosarcoma cells. Objective: To determine the expression of non-muscle myosin heavy chain 9 (MYH9) in osteosarcoma and its effect on the migration and invasion abilities of tumor cell. Methods: A total of 65 cases of osteosarcoma and 20 cases with benign osteochondroma who underwent resection operation in the Orthopedics Department of our hospital from January 1st 2009 to January 1st 2015 were selected. Their mR NA levels of MYH9 were tested by q rt-PCR. Immunohistochemical method was used to examine the expression of MYH9 in osteosarcoma and the correlation between the positive expression of MYH9 and the clinicopathological features of patients was illustrated by statistical analysis. MYH9 was compounded artificially. The expression of MYH9 in SAOS2 osteosarcoma cells was decreased by si RNA. Scratch test was used to determine the change of SAOS2 cell migration ability after MYH9 silence. Transwell assay was employed to detect the change of cell invasion ability after MYH9 silence. Results: The expressi on levels of m RNA of MYH9 and protein in osteosarcoma tissues were significantly higher than those in benign osteochondroma tissues. The high expression of MYH9 in osteosarcoma tissues was apparently related to the high Enneking classification (III classification) and lung metastasis. SiR NA of MYH9 The down-regulated expression of MYH9 could inhibit the migration and invasion abilities of SAOS2 cells. Conclusions: MYH9 shows a trend of high expression in osteosarcoma tissues, and its high expression is associated with features such as tumor invasion and metastasis. The down-regulated MYH9 can realize an anti-tumor effect by inhibiting the migration and invasion of osteosarcoma cells.