Formaldehyde (HCHO) greatly influences the human body, climate, and environment and is also an important intermediate product of the atmospheric photochemical reaction. As an important industrial area in Southwest China, Chongqing is the municipality with the largest population and the largest area in China. The backward energy structure and environmental protection facilities and the special terrain and climate characteristics, lead to serious air pollution. Therefore, it is of great significance to study the variation of formaldehyde concentration in Chongqing. In December 2018, a ground multi-axis differential absorption spectroscopy monitoring system (MAX-DOAS) was built in Phoenix Building, Jiangbei District, Chongqing, China. Combined with the spectral processing software QDOAS, the differential slant column concentration (DSCD) of formaldehyde is retrieved by nonlinear least square fitting algorithm, and the atmospheric quality factor (AMF) is obtained by geometric approximation method. Then the slant column concentration (SCD) of formaldehyde is converted into the column concentration (VCD). The analysis showed that the daily and weekly average changes of formaldehyde were similar. The minimum and maximum average concentrations of formaldehyde VCD were 0.982×10¹⁶ and 9.221×10¹⁶ molule·cm^-2, respectively. The average daily variation is obvious, higher in the morning and evening and the lowest at noon. It can be seen from the average weekly variation of formaldehyde VCD that the basic trend is consistent with the average daily variation. However, there was no obvious weekend effect and no obvious weekly cycle. Compared with the ground-based MAX-DOAS data and the TROPOMI observation of the satellite product (ozone monitoring instrument), the consistency between the two is good, and the correlation coefficient is 0.84. However, the value of TROPOMI was 21.5% lower than that of MAX-DOAS. The results show that the ground-based MAX-DOAS can provide an effective means for the real-time and rapid monitoring of urban regional pollution gases such as HCHO and the research and analysis of the change law, and can also effectively verify the satellite data sources.