Objective It was to assess the application value of LAVA-FLEX sequences in determining the type of anal fistula and it was also to study the characteristics in dynamic inhancement phases. Methods 31 patients with surgically proved anal fistula underwent MRI examination.The following sequences were obtained: sagittal T2WI/FS、T2WI/ FS axial、T2WI/FS coronary、DWI、LAVA-FLEX, sagittal、axial and coronary LAVA-FLEX + C. Statistical analysis with surgical results was refered as standards.The value of MRI with various sequences in the diagnosis of various types of anal fistulas and their enternal openings was statistically analyzed according to surgical results. SPASS 17.0 software package was used to perform X2 test,t test,analysis of variance and there was statistically significant(P<0.05). Results On the display for internal openings and anal fistula,it showed highest rates reaching up to 88.09% and 87.8% in the AX LAVA-FLEX +C.It showed 8 sequences as follows: AX LAVA+C、COR LAVA+C、AX DWI、 SAG LAVA+C、AX T2WI/FS、COR T2WI/FS、SAG T2WI/FS、AX LAVA.It performed X2 test, the results of interal openings: X2 =28.886,P1=0.000, P1<0.001,the results of anal fistula: X2 =42.352,P1=0.000, P1<0.001, The difference was statistically significant. LAVA-FLEX inhanced sequence was better than T2WI/FS(P=0.006、0.005), there was statistically significant difference.It was compared with 6 phases ,contrast noise ratio showed from high to low equilibrium phase、venous phase、late arterial phase、 coronal phase、early arteral phase、sagittal phase、plain phase. Conclusion It showed highest rate in AX LAVA+C for kinds of sequences in MRI for ana fistula. It showed highest for contrast noise ratio in the equilibrium phase.