The invention provides a non-intrusive monitoring method. The method comprises the following steps of: obtaining business data of a terminal by a server; reporting the obtained business data to a front-end cache; transmitting the business data of the front-end cache into a cache for monitoring; obtaining business data in the cache for monitoring according to a preset monitoring sampling time length, and accumulating the business data to obtain a monitoring data amount; and when the obtained monitoring data amount is smaller than a preset alarm lower limit value or greater than a preset alarm upper limit value, sending alarm information. Due to the setting of the front-end cache and the cache for monitoring, the business data is obtained through the front-end cache and then transferred into the cache for monitoring as soon as possible, and a monitoring code does not need to be implanted into the business system and the business system does not need to be modified, so that non-intrusive monitoring is realized. According to the method, a monitoring program and a main program are separately operated, so that the condition of influencing the operation of the main program as the main program spends a long time to call an external monitoring program and the monitoring program has problems is avoided.