We report a high-power thin Nd:YAG slab laser with slab dimension of 1 mm \time 10 mm \time 60 mm partially edge-pumped by diode laser arrays. Passive Q-switching is achieved with a Cr4+:YAG microchip adopted as the saturable absorber mirror. The pulse duration is around 10 ns while the pulse repetition rate is higher than 10 kHz. The average output power of 70 W is obtained with a slope efficiency of 36%. The diffraction limited beam quality in the thickness direction is obtained by controlling the pump beam diameter inside the slab. The laser head is very compact with size of only 60 \time 70 \time 150(mm).