Document and Entity Information - shares
9 Months Ended
Sep. 30, 2017
Dec. 04, 2017
Document And Entity Information    
Entity Registrant Name CM Seven Star Acquisition Corp  
Entity Central Index Key 0001713539  
Document Type 10-Q  
Trading Symbol CMSS  
Document Period End Date Sep. 30, 2017  
Amendment Flag false  
Current Fiscal Year End Date --12-31  
Entity a Well-known Seasoned Issuer No  
Entity a Voluntary Filer No  
Entity's Reporting Status Current Yes  
Entity Filer Category Smaller Reporting Company  
Entity Common Stock, Shares Outstanding   26,323,092
Document Fiscal Period Focus Q3  
Document Fiscal Year Focus 2017