The invention relates to a generating set temperature detection system based on compound digital filtering, comprising a temperature sensor circuit, a signal conditioning and A/D conversion unit, and a microprocessor, employing a one-chip microcomputer as a microprocessor chip to control a sampling frequency and an A/D conversion frequency, and embedding a temperature information quantity compound digit filtering unit. An operation unit is based on an improved small sample Grubbs' criterion to discriminate time-invariance data, and combines with a first order difference filtering method to eliminate gross of time variable data, thereby discarding or replacing unreasonable data. According to engineering applications, the system has the characteristics of simple and effective structure, high operation efficiency, sound filtering effects of static and dynamic tests, and accurate and stable output temperature, and meanwhile provides reliable data for temperature control of a top layer.