The orientation dependence of the piezoresistive effect of p-type single crystalline 3C-SiC thin film grown on a (100)Si wafer was characterized. The longitudil, transverse gauge factors in [100] orientation, and longitudil gauge factor in [110] orientation were found to be 5.8, 5.2, and 30.3, respectively. The fundamental piezoresistive coefficients p11, p12, and p44 of p-type 3C-SiC were obtained to be 1.51011 Pa1, 1.41011 Pa1, and 18.11011 Pa1, respectively. From these coefficients, the piezoresistive effect in any crystallographic orientation in p-type single crystalline 3C-SiC can be estimated, which is very valuable in designing micro-mechanical sensors.