Abstract: In this experiment,La0.67Ca0.33MnO3 films grown on different canted LaAlO3 substrates were tested with different bias currents.The results found are:① the temperature of the peak resistance decreases obviously due to the Joule heat effect when the current is lager than 1mA;② the maximum resistance in R-T curves is reduced with the current increasing when the current is less than 1mA.This is a deviation from the Ohm’s law(namely nonohmic behavior);③ the nonohmic behavior become larger with the canted angle increasing.By analyzing,two results were obtained:① Joule heat effect causes the transit temperature TM-I to decrease;② nonohm behavior in films is possibly caused by the grain boundries as tunneling resistance junctions.