Stop-and-check (including questioning) is one of the means by which the police perform their duties. It is targeted at passersby and vehicles on the road and can be basically divided into three types: identity check, check for traffic violations, and check for prohibited articles. As such, it has both the administrative attribute of prevention of danger and the judicial attribute of investigation after the event. Stop-and-check may easily lead to search, examination, seizure, retention, even detention. Stop-and-check should take the principle of law reservation as its basis, be subject to the principle of proportionality, and conducted in a prudent and restraint manner in accordance with law. In the policing practice, stop-and-check are initiated frequently and carried out in many different ways, but its basis of legal authorization is vague, general and fragmented. China should adopt the attitude of filling in the gaps and making up for deficiencies towards the practice of stop-and-check, draw on foreign experiences, and regulate and supervise the practice at both the substantive and the procedural levels, namely give a satisfactory answer to the questions of “why carry out the check?” “what to check?” and “how to check?” Generally speaking, stop-and-check should take “suspicion” as its substantive ground and procedural supervision over stop-and-check should take the determination of whether there is a genuine “suspicion” as it core content.