The invention discloses a test method and device for simulating thermal WHTC circulation in diesel hot and cold WHTC circulation. The test method comprises the following steps that test conditions aremet by controlling the lower air
inlet temperature, air inlet vacuum degree, post-intercooling temperature and exhaust
back pressure under rated conditions of a
diesel engine according to rules; according to a WHTC circulation program set by a gantry, circulation conditions in the WHTC circulation program at the last 600+ / -10s are selected for testing to pre-process an SCR catalyst unit; after the SCR catalyst unit is preprocessed,
diesel engine hot dipping is carried out immediately for 10+ / -1min to serve as pro-
processing of a
diesel engine hot start WHTC circulation test; the steps of a formal thermal WHTC circulation test involve that a gantry WHTC circulation program is started immediately after a hot dipping period is completed for the formal thermal WHTC circulation test, thereforethe temperature of a thermal WHTC circulation SCR catalytic unit is consistent with the temperature of the thermal WHTC circulation in the hot and cold WHTC circulation, the efficiency of the SCR catalyst unit can be fully utilized, the consumption of
urea can be reduced, the energy is saved, the environment is protected, and a large amount of test time can be saved.