In the dry cropping lands, soil rewetting due to precipitation can stimulate soil CO₂ efflux pulses, which is called the "Birch Effect". Two types of responding mechanisms:"Substrate supply" and "Microbial stress", were proposed to explain the soil "Birch effect". To elucidate how precipitation change affects the "Birch effect "and its responding mechanism, we conducted precipitation simulation experiments in a winter wheat field to measure the short-term response of precipitation levels(1-32 mm) on soil respiration from 0 to 72 h at the jointing stage and during the summer fallow period on the Loess Plateau. The results showed that soil respiration peaked at 4 h with 1 to 16 mm of precipitation, but the peak was delayed by another 4 h at 32 mm precipitation. Higher precipitation delayed, but increased soil respiration compared to lower precipitation. The peak value for the soil respiration rate(SR-P) increased exponentially with increased precipitation(P)(jointing:SR-P=0.97P^0.09, R²=0.5, P < 0.05, fallow:SR-P=1.07P^0.09, R²=0.98, P < 0.01). Cumulative soil respiration after 72 h(CO₂-P) increased linearly with the precipitation level(jointing:CO₂-P=0.03P+5.99, R²=0.58, P < 0.05; fallow:CO₂-P=0.11P+6.04, R²=0.86, P < 0.01). The temperature sensitivity of soil respiration(Q₁₀) was correlated binomially with the precipitation level(jointing:Q₁₀=-0.007P²+0.2P+0.7, R²=0.32, P < 0.05; fallow:Q₁₀=-0.01P²+0.3P+0.2, R²=0.86, P < 0.01). Stepwise correlation analysis between soil carbon fractions and soil respiration rate showed that soil respiration rate was significantly correlated with soil microbial biomass C at the jointing stage for all precipitation levels, indicating that a "microbial stress" mechanism dominated the "Birch effect" during growing season. However, during summer fallow period, soil respiration rate was significantly correlated with microbial biomass C, which suggested "microbial stress", when the precipitation amount was lower than 8 mm, but correlated with chloroform-fumigated extracted C, which suggested that both mechanisms were operating when precipitation amount was equal to 8 mm. However, soil respiration was significantly correlated with K₂SO₄-extracted soil C when precipitation amount was equal to or higher than 16 mm, indicating a shift to the "Substrate supply" mechanism. Compared with that during the summer fallow period, the soil "Birch effect" was weaker and its responding mechanism had changed at the wheat jointing stage due to root respiration and shading effects.