The invention discloses helium mass spectrum leakage detection equipment for a nuclear evaporator heat conduction pipe and a quantitative positioning method. The equipment comprises an air source, a helium source, an air distributor, an injector and a gas distributor from upstream to downstream in sequence, and further comprises a diffuser, a sampling tool shelf, a mass spectrometer, a control cabinet and a computer. The diffuser is used for purging, the sampling tool shelf and the mass spectrometer are used for pumping and collecting gas, the control cabinet is used for analyzing data of the mass spectrometer or controlling the environment, and the computer is used for achieving man-machine interaction. The equipment can safely and accurately collect gas and analyze gas content and content changes, the number and positions of leakage points can be worked out with a leakage detection method, leakage detection time can be greatly shortened, and cost can be saved.