Improvised explosive devices (IED) and homemade explosives (HMEs) have become the preferred choice for terrorists and insurgents. It's a challenge to develop the techniques to detect explosive hazards at standoff distances. In this paper, a standoff UV Raman spectrum detection system for explosive detection was developed, which can realize 2-10m Raman spectrum detection of solid, solution and trace potassium nitrate samples. The relationship between Raman signal intensity (RSI) and pulse energy, detection distance and sample concentration was studied. The experimental results show that the RSI is approximately proportional to the pluse energy and contains nonlinear terms. It has an inverse square relationship with the detection distance and a linear relationship with the sample concentration. The concentration of solution and trace potassium nitrate samples of were successfully predicted at 2m distance, and the root mean square error of prediction (RMSEP) was 11.7 and 6.1, respectively.A simple and effective method for preparing trace potassium nitrate is presented. Copyright © 2021 SPIE.